Dyes

DYES, chemical substances possessing the property of coloring other objects in their own or another color directly or with the help of another chemical compound—a mordant. The widespread use of dyes, it must be assumed, is caused by man's instinctive striving for a variety of visual color impressions, which play a role in creating certain conditioned reflexes for various life processes: eating, sleeping, working, entertainment, and moods (joy, grief, a call to struggle, etc.). This need is the main stimulus for the fact that man paints the walls of his dwelling, wallpaper, furniture, clothing, footwear, food products, drinks, dishes, toys, books, paintings, etc. The property of dyes of various colors to absorb and reflect a greater or lesser amount of falling light and heat rays is widely used by man for regulating the natural and artificial lighting of dwellings and for facilitating the thermoregulation of the body by means of light or dark clothing at different times of the year. Some dyes find application in medicine, in analytical chemistry as indicators, in histology (see Histological technique), in bacteriology, and in chemotherapy. Sometimes a dye itself is colorless but produces coloration of an object after appropriate processing of it. Every dye absorbs a part of the rays of the visible part of the spectrum, by virtue of which it has its own "absorption spectrum," which determines the characteristic visible coloration of the substance in a color complementary to the one absorbed. According to Bernstein, all dyes can be classified as follows. I. Inorganic coloring substances. 1. Natural mineral, or earthy dyes (chalk, ocher, mummy, sienna, and a multitude of others). 2. Artificial mineral dyes (salts and oxygen compounds of mercury, cadmium, copper, tin, antimony, zinc, cobalt, manganese, iron, etc.). II. Organic coloring substances. 1. Natural, i.e., occurring in nature: a) Dyes of vegetable origin, e.g., indigo, carthamin, madder, litmus, alkanin, as well as many uninvestigated coloring substances from the berries of bird cherry, blueberry, cherry, blackberry, etc.; b) Dyes of animal origin: carmine from cochineal (Coccus cacti), kermes from Coccus ilicis, purple from the red murex (several species of mollusks Purpura), one of the most ancient dyes; Indian yellow (piuri, purree) from the urine of cows fed with the leaves of the mango tree (Mangifera indica). Many natural organic dyes are so well studied that an attempt has been made to provide a rational classification for them. They can be divided into the following 9 groups: 1) xanthone group (euxanthic acid), 2) flavone (hematoxylin, brazilin, luteolin), 3) flavonol (quercetin, rhamnetin, fisetin), 4) anthraquinone (carminic acid, alizarin, alkanin), 5) indole (indigoids), 6) quinoline (berberine), 7) coumarone (catechin), 8) orcin (azolitmin, orcein), 9) naphthalene (juglone, lapachol). For many natural organic dyes, only empirical formulas are given. 2. Artificial organic dyes. All artificial organic dyes available for sale are prepared from materials obtained from coal tar, which is why they also bear the name coal-tar dyes. The chemistry of artificial organic dyes began to develop relatively recently; in 1856, Perkin obtained the first artificial dye—mauveine, or the so-called Perkin's violet. At the present time, such dyes number over 1,500 names. Natural organic dyes do not differ in structure from artificial ones, and at the present time, many dyes, e.g., indigo and alizarin (madder), can be obtained synthetically. Many other artificial dyes, although they bear the names of natural ones, for example, orchil, Indian yellow, brown catechu, are similar to them only in the color of the provided tint, but are not identical in structure; therefore, the old division of dyes into natural and artificial must be preserved until the structure of natural dyes is finally clarified. The presence of known atomic groups in a particle of organic matter determines the coloring properties. If a known atomic group is introduced into a particle of a colorless compound, a colored substance will be obtained, devoid of the ability to dye. Such atomic groups, which impart coloration to substances, were named by O. N. Witt as chromophores, or color-bearing groups. Such chromophores include: 1. Quinoid groupings: =( )= and | 2. Ethylene groups: -CH-CH- 3. Adjacent carbonyl groups: -CO-CO- 4. Azo groups: -C-N=N-C- 5. Azo-oxy groups: -N=N- 6. Nitroso group attached to carbon: -C-N=O 7. Nitrogen-carbon groups: >C=N- or >C=NH

8. Nitro groups: -NO₂. 9. Sulfur-containing groups: -C-S-S-C-, -C-S-S-O-, etc. When such groups are introduced into colorless hydrocarbons, benzene, naphthalene, anthracene, aniline, etc., colored compounds are formed that can produce entire series of dyes, which is why such colored compounds are called chromogens. But such substances—chromogens—are not dyes. To convert them into true dyes, i.e., to impart coloring ability to them, it is necessary to introduce auxiliary groups into the benzene nuclei: alkyl (CH₃), amide (NH₂), hydroxyl (OH), carboxyl (COOH), sulfo-groups (HSO₃), halogens, etc. Such groups, which turn a colored substance into a dye, are called auxochromes. For example, C₆H₅-N=N-C₆H₅, azobenzene, although it contains the chromophore -N=N-, is not a dye, but a chromogen; by introducing the auxochrome NH₂, we obtain the dye amido-azo-benzene (C₆H₅-N=N-C₆H₄NH₂). From each chromogen, two series of dyes originate depending on the auxochromic group: acidic upon the introduction of OH, HSO₃, COOH groups, and basic upon the introduction of NH₂, NHCH₃, N(CH₃)₂ groups, for example, amido-azo-benzene—basic (see above) and oxy-azo-benzene—acidic (C₆H₅-N=N-C₆H₄OH). If several auxochromic groups are introduced into a particle of a coloring substance, this always leads to a change in color or its intensity and an increase in the coloring power of the given substance. For example, amido-azo-benzene is a yellow dye, diamido-azo-benzene is orange (chrysoidine), triamido-azo-benzene is brown (Bismarck brown, or vesuvine). The position of the auxochromic groups (para-, ortho-, or meta-) also plays a large role in the change of intensity and color of dyes. The color of dyes is intensified and changed by the introduction of several identical or several different chromophoric groups. Upon reduction, dyes turn into colorless leuco-bases, which are converted back into dyes upon oxidation. When classifying coloring substances according to the generally accepted proposal of Witt, one is guided by the composition of the chromophoric groups. 1. Nitroso-dyes, or quinone-oxy-pigments: chromophore -N=O. Not used in medicine. 2. Nitro-dyes: chromophoric group -NO₂, e.g., picric acid—trinitrophenol; aurantia—hexanitrodiphenylamine. 3. Azo- and diazo-dyes: chromophore -N=N-; e.g., basic—chrysoidine, Bismarck brown, or vesuvine; acidic—methyl orange, tropaeolin. 4. Oxy-azo-dyes: chromophore -N=N-. 5. Diphenyl- and triphenyl-methane dyes; they yield the following groups: a) diphenyl-methane dyes: chromophore >C=N-, e.g., auramine (Pyoctaninum aureum); b) triphenyl-methane dyes: α) diamino-triphenyl-methane dyes (malachite green group), e.g., malachite green—tetramethyl-diamido-triphenyl carbinol; brilliant green—the same as malachite green, but a tetra-ethyl derivative; β) triamino-triphenyl-methane dyes (rosaniline group), e.g., fuchsin—trimethyl-rosaniline, methyl violet—pentamethyl-rosaniline (the same as Pyoctaninum coeruleum); aniline blue—triphenyl-rosaniline, acid fuchsin—sodium salt, di- and tri-sulfonic acids of fuchsin; γ) tri-oxy-triphenyl-methane dyes (aurin group), e.g., aurin, rosolic acid, corallin—di-oxy and tri-oxy-triphenyl-methane; δ) derivatives of triphenyl-methane-carbinol-carboxylic acid (phthalein group), e.g., fluorescein, eosins, pyronine. 6. Quinone-imide dyes yield a) thiazines: chromophore—a nitrogen atom connected to two aromatic radicals, which in turn are connected to a sulfur atom; e.g., thionine, methylene blue—tetramethyl-thionine chloride, methylene violet (dimethylthiocoline); b) azines: chromophore—a tetra-atomic group >N-N< connects two di-atomic aromatic radicals. E.g., neutral red (toluylene red), safranines, indulines (nigrosine). 7. Indigo pigments: tetra-atomic chromophoric group >C=C<, representative—indigo blue. 8. Sulfur dyes: chromophoric group -S-S- or >C=S; a significant number of dyes of various shades, mainly brown and black; not used in medicine. From a practical standpoint, all dyes can be divided into 8 classes: 1) Acidic: sodium salts of sulfonic acids, carboxylic acids, or nitro compounds. They dye wool and silk in an acid bath directly: eosin, picric acid, most azo dyes. 2) Tannin: usually hydrochloride salts of bases. They dye wool and silk directly, and cotton with the help of tannin (fuchsin, auramine). 3) Salt, dyeing with the addition of neutral or alkaline salts to the bath. Benzidine dyes belong here. 4) Sulfur dyes, dyeing cotton in a bath with the addition of sulfur compounds. 5) Mordant—all of a phenol-like or acidic nature, fixed on the fiber only with the help of mordants; alizarin dyes, plant dyes, etc., belong here. 6) Vat, having no affinity for fibers; they are fixed on them with the help of reduction and subsequent oxidation (indigo). 7) Developed; they are not used in finished form due to their insolubility in water, but are formed directly on the fiber, e.g., aniline black, nitraniline red azo dye. 8) Pigment; they are glued to the fiber or surface with various substances, albumin, oil, etc. Most mineral dyes belong here. Organic dyes, both natural and artificial, that provide a fast color only with the help of mordants, with which they form insoluble dye lakes, are called adjective; those that dye without mordants, directly, are substantive. Mordants are mineral and organic. Mineral mordants include antimony, arsenic, copper, lead, mercury, chromium, nickel, alumina, iron, and tin salts. In this case, different colors and shades are obtained from the same dye with different mordants; organic mordants are of animal (albumin, glue, alkaline solution of silk) and vegetable origin (sesame, rapeseed, olive, castor oil, tannin, tanning substances). Fabrics are first mordanted and then dyed (immersion method); sometimes this is done simultaneously (steaming method). Dyes fixed by mordants are rarely dangerous to health, but sometimes they can still pass into a soluble state and irritate the skin, e.g., dyes with arsenic, chromium, or antimony mordants. Such a transition is facilitated by prolonged exposure to sweat, fatty acids, and rubbing into the skin. Therefore, for prophylactic purposes, one should avoid underwear made of colored fabrics. Various mineral substances are often added to dyes, especially artificial ones, sometimes for the purpose of falsification, sometimes for dilution (blending), e.g., sodium sulfates and carbonates (up to 50% in indigo carmine), calcium, iron, aluminum, salts of tartaric acid, ammonium (up to 17% in cochineal), or organic substances (dextrin, glue, sugar, etc.). In vegetable dyes, residues of the materials from which they are extracted or with the help of which they are processed are often found. In natural organic dyes, up to 10% ash is sometimes found (Dobrynin). The result of the great demand for dyes was the colossal growth of the dye industry. The number of dyes, natural and artificial, exceeds 2,000; the largest part of them belongs to artificial organic coal-tar or aniline dyes (see Aniline, aniline dyes). Thanks to the successes of chemistry and technology, artificial dyes are increasingly displacing natural organic dyes from practice. Some active principles of the latter, e.g., alizarin, indigotin, have already been obtained synthetically. The first replaced the vegetable dye madder (garance), the second—vegetable indigo. Expensive cochineal is being displaced by cheap azo dyes. Conversely, logwood and catechu have not yet lost their significance to this day, and quercitron is also still widely used for dyeing wool, and weld for calico; but the main field of application for natural organic dyes, where they have fully retained their significance, is food products and beverages. Of the few dyes of animal origin (cochineal, kermes, and lac dye, extracted from insects; purple—from snails; sepia—from cuttlefish; lutein—from chicken eggs), only cochineal and kermes currently find more or less significant application. Of the vegetable dyes, the total number of names of which does not exceed 50, the following have the greatest application: extracted from wood—sandalwood, logwood (blue sandalwood), coloring substances of brazilwood (red sandalwood), fustic and yellow wood; from bark—quercitron; from leaves and stems—orsein, litmus, indigo, chlorophyll, woad, sorghum, chika, purree, chrysin; from sap—catechu (cutch), kino, aloe, gamboge; from flowers—coloring substances of mallow, safflower, saffron, marigolds; from roots—turmeric, alkanet, madder (garance), berberine, lokao; from root vegetables—coloring substances of beets, carrots; from fruits—annatto, weld; coloring substances of orange, lemon, grapes, blueberries, cherries, raspberries, etc. Finally, bacterial pigments. Caramel, burnt coffee, and roasted starch belong to the group of vegetable dyes.

Among plant dyes, very few are poisonous: gamboge, phytolacca, bloodroot (Zatex sanguinaire), monkshood flowers (Aconitum napellus), and (according to Swiss legislation) berberine from barberry roots. Of the dyes mentioned above, the following deserve separate description: Persian berries; obtained from Avignon (Persian, yellow) berries, plants of the genus Rhamnus. There are many varieties depending on the plant species and place of growth. Persian berries are widely used for dyeing calico in the form of a lake with a tin mordant. A brownish-green extract of Persian berries mixed with quercitron and fustic with an alum mordant is used in painting and wallpaper manufacturing. The active principle is in the form of the glycoside xanthorhamnin, which is decomposed by boiling with H₂SO₄ into rhamnose and the true dye rhamnetin: C₁₆H₁₂O₇. Alkanna; a dye obtained from the roots of the European plant Alcanna tinctoria or the African Lacosinia alba. The dye is extracted after boiling the roots in water with gasoline in the form of an oily extract. The active principle 'alkannin', C₁₅H₁₄O₄, is red in color; it is obtained by treating the extract with caustic potash and precipitating with HCl. It is used mainly in perfumery for coloring pomades, tinctures, etc. An alcoholic solution of alkanna gives absorption bands in the spectrum corresponding to wavelengths (λ) 523.1; 563.8; 545; 487.1; 456 mµ. The spectrum does not change with acid, but with NH₃ it is: 634.5; 584.5. Gamboge - a poisonous yellow dye obtained from the resin of the Ceylonese plant of the genus Garcinia Morella or Hebradendron gambogioides, it possesses strongly drastic properties. An intake of 3-4 g is fatal to humans. It is used mainly in painting and the paint industry, but sometimes it is also used for coloring candies, which is completely unacceptable. With water, it gives a bright yellow emulsion. Indigo; obtained from plants of the genus Indigofera. Indigo is used for the blue dyeing of wool and paper. Dyeing is performed with a leuco-compound, and a durable blue color is obtained on the fabric by oxidizing the latter. Kobert considers indigo, based on experiments on rabbits' eyes, not to be indifferent to the organism. The active principle is found in plants in the form of a glycoside, colorless indigo, which decomposes into glucose and indoxyl; the latter, upon oxidation, gives blue indigo (indigotin) (C₆H₄CO.NH)₂C₂, also obtained synthetically by Baeyer. Indoxyl in the form of indican (see) is contained in urine. In rare cases, the indigotin formed from indican can cause the urine to turn blue. A solution of indigotin in concentrated H₂SO₄ gives an absorption band in the spectrum for λ = 635.5 mµ, in a fresh chloroform solution for λ = 605.8 mµ, and after a short time, another band appears for λ = 565.8 mµ. Indigocarmine, the sodium salt of disulfoindigotic acid, a blue-violet powder, is used for coloring food products and beverages green, which is obtained by mixing indigocarmine with turmeric or saffron. Catechu (or cutch) is the dried juice of various species of Indian acacias of a dark brown or yellow color. The active principle—catechin, or catechu-tannic acid—is a pentahydric phenol that forms japonic acid upon oxidation. It is widely used for dyeing fabrics a reddish-brown color when treated with a chrome mordant, and a greenish-brown color with an iron mordant. The colors are distinguished by great durability. Catechu is often used for coloring tea and other beverages. The absorption bands of a strong alcoholic solution correspond to λ = 652.6; 578.2 mµ. Acids do not change them; NH₃ increases the intensity of the absorption bands. Quercitron—a coloring extract from the bark of the oak Quercus tinctoria—is used for calico printing as an adjective dye in the form of orange-yellow lakes with a tin mordant and greenish-yellow with an alumina and chrome mordant. From quercitron, the glycoside quercitrin is obtained, which contains the true dye quercetin. The latter corresponds to flavin, the coloring power of which is 16 times greater than that of quercitron. Flavin is widely used for dyeing wool. It does not give absorption spectra. Kermes; this name refers to two dyes: one (according to Lehmann) is obtained from the American grape Phytolacca decandra. The beautiful red-violet berries of this plant, cultivated in the south of Europe and in the Caucasus for coloring wines, are poisonous due to their drastic action. The solution takes on a pink or lilac color from the action of NaHCO₃ and borax (Khlopin). The other red dye—oak kermes—is obtained from the dried females of insects living on the holm oak (Quercus ilex) in southern France. Cochineal—a red dye obtained from the insects Coccus cacti (lac-dye), living on cacti in Mexico, Java, and other places. The tin lake of cochineal for wool and silk is still considered the best dye for durability and beauty. By precipitating an alkaline decoction of cochineal with acids, red carminic acid (C₁₂H₂₂O₁₃) is obtained, which is a derivative of anthraquinone. Carmine is widely used in histological microtechnique. Cochineal is used as an indicator in acidimetry, and also for coloring wines, candies, meat, and sausages. The absorption bands of carmine correspond to λ = 497.0; 533.0; 468.8 mµ in aqueous solution; in ethyl alcohol λ = 499.2; 535.7; 470.7 mµ. The spectrum does not change with acids; with NH₃, the aqueous solution shows an absorption band at λ = 570.7; 528.5; 494.8. Madder (rubia) is obtained from the ground roots of the plants Rubia tinctorum. This dye was known to the ancient Egyptians. Its active principle—alizarin—is contained in the form of glycosides (ruberythric acid). In 1869, Graebe and Liebermann first obtained alizarin synthetically, and at the present time, artificial alizarin has almost completely replaced natural dye. Alizarin with various mordants gives different lakes: with alumina—red, with iron salts—violet, with lead acetate—blue-violet. The absorption bands in an alcoholic solution of caustic potash correspond to λ = 579.5; 625.5; 539.2 mµ. Turmeric (yellow ginger)—a substantive brown dye obtained from the rhizome of Curcuma tinctoria. It is widely used for coloring butter, tea, coffee, candies, and bakery products. Sometimes it serves for dyeing silk a greenish-yellow color. It is also used as a reagent for free alkalis and boric acid. The coloring principle—curcumin C₁₉H₁₄O₄(OCH₃)₂—is a β-diketone. Aqueous solutions of turmeric give a darkening of the green, blue, and violet parts of the spectrum; NH₃ does not change the spectrum, KOH gives a wide blurred band in the blue part. Litmus—a coloring substance of lichens of the genus Lecanora—is widely used as an indicator; the absorption bands of an aqueous solution correspond to λ = 579.5; 611.7; 536.5 mµ. Annatto is obtained from the pulp of the seeds of the fruits of Bixa orellana. A substantive dye for cotton fabrics of an orange color. It is usually used for coloring butter, cheese, less often candies, etc. The active principle is bixin C₂₈H₃₄O₅. The absorption bands of annatto in ethyl alcohol correspond to λ = 459.6; 492.7; 424.3 mµ. Orseille (orchil)—a substantive dye obtained from American lichens of the genus Roccella. To obtain a blue-red dye, the lichens are infused with ammonia water. The preparation in the form of a powder under the name of French purple serves for dyeing silk and wool a beautiful and durable purple color. Orseille is also used for coloring wine and candies. Persio dye is similar to orseille, obtained from lichens of the genus Lecanora. The orseille aqueous extract gives absorption bands for λ = 582.0; 537.5; 498.5 mµ; in the presence of acid, a wide band for λ = 512.8, a narrow one for λ = 594.3 mµ. Sandalwood (sandal)—a red coloring substance from the wood of the sandalwood tree Pterocarpus santalinus. The active principle is santalin C₁₅H₁₄O₅. It dissolves very poorly in water, easily in alcohol. Sandalwood with a chrome mordant is used in the dyeing industry for dyeing brown, with an alumina mordant—blue-red. The absorption bands in an alcoholic solution correspond to λ = 507.2; 472.0; 442.9 mµ. Safflower is obtained from the dried flowers of Carthamus tinctorius. A substantive, non-durable pink dye used for coloring candies and as a vegetable rouge with the addition of talc. Safflower carmine is obtained from the dye by boiling with soda and precipitating with acetic acid. The active principle: carthamin C₁₄H₁₆O₇. The absorption bands of an aqueous solution of safflower carmine correspond to λ = 558.8; 517.4; 485.0 mµ. Fernambuc wood (or red sandalwood), containing the glycoside brazilin, analogous to the hematoxylin of logwood, which upon oxidation turns into brasilein C₁₆H₁₂O₅+H₂O. With a chrome mordant, it gives a red-brown color, with alumina—blue-red.

The absorption bands in ethyl alcohol correspond to λ=525.8; 487.8; 456.1 mμ. Chlorophyll is a coloring substance from the green parts of plants. It is used for coloring liqueurs, essences, confectionery, and perfumery products. The absorption bands of a strong alcoholic solution correspond to λ = 664.2; 614.1; 584.5; 537.5 mμ; for a diluted solution, the weak bands disappear, and the first one becomes narrower. Saffron is dried, tangled threads about an inch long from the stigmas of the flowers of the plant Crocus.

DYES

sativus, growing in Persia, Africa, and Southern Europe, of a brown or dark orange color. It is very widely used for coloring dough, butter, candies, and tea. It is distinguished by a bitter, spicy taste and an aromatic odor. It contains the active principle in the form of the glycoside crocin, essential oil, and sugar. Saffron is attributed with the property of soothing pain and convulsions and inducing menstruation. The absorption bands of an aqueous solution of saffron correspond to λ=475.1; 443.9 mµ; acids and NH₃ do not change the spectrum. Due to the fact that the majority of natural organic dyes, with very few exceptions, are harmless when ingested, sanitary legislation treats the coloring of food products and beverages with natural dyes much more leniently than with coal-tar dyes. Regarding aniline dyes, the German law of 5/VII 1887 makes a distinction between harmful and harmless ones. However, for meat, sausages, lard, milk, and wine, it prohibits any coloring whatsoever. When coloring flour, pasta, honey, canned vegetables and fruits, fruit juices, and spices with permitted dyes, the law requires a declaration. Regarding the coloring of cheese and butter with harmless dyes, there are no prohibitions or restrictions. The coloring of margarine, sugar (with ultramarine), vinegar, and vodkas (with caramel) is permitted. The circular of the People's Commissariat of Health and the People's Commissariat of Justice of the RSFSR No. 32 of 4/II 1925 states: "In order to prevent the coloring of food and flavoring products and beverages with dyes that could harm the health of the consumer, in cancellation of the circular of the People's Commissariat of Health 'On the prohibition of the use of coal-tar dyes' No. 261 of 10/X 1922 (Bull. of the People's Commissariat of Health No. 18-19, 1922), the following rules are established: 1. The use of mineral and coal-tar dyes (aniline: azo dyes, etc.) and any other dyes, except those listed in clause 2, is prohibited for coloring food, flavoring products, and beverages (cheese, butter, candies, gingerbread, fruit and berry waters, etc.). 2. The following dyes are permitted for coloring the products mentioned in the previous clause: red dyes: cochineal, carmine, juices of edible berries (cranberry, raspberry, strawberry, blueberry, red and black currant, etc.), decoction of Brazilwood, malvin (from mallow flowers), acid litmus; yellow dyes: saffron, Avignon and Persian berries from the plant Rhamnus tinctoria, yellow ginger, turmeric, annatto, yellow sandalwood; blue dyes: indigo, indigo carmine, alkaline litmus, ultramarine in special packaging with a designation that it contains no harmful impurities; green dyes: chlorophyll, mixtures of the yellow dyes mentioned above with permitted blue ones; violet dyes: logwood and mixtures of the red and blue dyes mentioned above; brown dyes: burnt sugar, toasted starch, roasted coffee; white dyes: starch, powdered sugar. 3. The preparation of dyes intended for coloring food products and beverages is permitted both in the establishments preparing the food and flavoring products and beverages themselves, and in special factories, and in either case, permission from the provincial and regional health departments (via the sanitary-prophylactic sub-department) must be obtained. 4. The manufactured product must be released in special packaging with the designation of the dye and with the note 'permitted for coloring food products and beverages... by the provincial, regional health department under No... of... month... year'. 5. Dyes of foreign production, released even under the names of the listed permitted dyes, are allowed for sale only after laboratory control by the provincial, regional health departments or, in the absence of such, in a laboratory designated by the latter. Note: in case of difficulties in providing a conclusion, the provincial, regional health departments shall forward the matter for resolution to the People's Commissariat of Health (via the sanitary-epidemiological department). 6. Supervision over the execution of these rules is entrusted to the sanitary bodies of the People's Commissariat of Health in the center and in the localities. 7. Those guilty of violating clause 1 of these rules are punished under Article 191 of the Criminal Code; those guilty of violating clauses 3 and 4 under Article 141 of the Criminal Code, and those guilty of violating clause 5 under Article 139 of the Criminal Code." Due to the categorical prohibition by the legislation of the RSFSR of coal-tar dyes for coloring food products, sanitary control over the coloring of food substances in the USSR must be directed first and foremost towards being able to distinguish coloring with natural organic dyes from aniline dyes. For this purpose, one first utilizes the property of coal-tar dyes to intensely color wool and cotton threads. The dye is extracted from the object with some suitable solvent (distilled water, ether, acetone, alcohol, etc.), the extract is filtered, evaporated, and dissolved again in water or 10% alcohol. After adding KHSO₄ to the solution, several threads of white degreased wool are immersed and boiled for 10 minutes (Arata's method). Sometimes, instead of wool, it is necessary to use cotton threads, degreased and mordanted (with a 1.0% solution of alum and a 10% solution of sodium acetate). Coal-tar dyes give a bright color to the threads, which is not washed off by water, while natural organic ones give a weak color or one that is washed off by warm water. Instead of threads, one can use preparations of fresh yeast fixed on cover glasses (Carpene's method), keeping them (without heating and KHSO₄) in the obtained solution for 4 hours. To distinguish dyes, one can also use the method of determining electrical conductivity. Khlopin and Vasilyeva found that solutions of coal-tar dyes, ceteris paribus, give significantly higher electrical conductivity than natural organic dyes. More precise methods for distinguishing natural from artificial dyes are the individual identification of dyes with various reagents according to the methods of Leeds, Speth, Weingärtner and Witte, Gommel and Gnehm, Roth, etc. As examples, the tables of Leeds and Speth for the identification of certain dyes are provided here. There also exists the spectroscopic method of Formanek, which is very sensitive and fast, based on finding characteristic absorption bands, but it is unsuitable for the identification of yellow, brown, and black dyes. The number of absorption bands and their location are given in the special tables of Formanek, attached to his special spectroscope (from the Krüss firm in Hamburg); shifts and changes in absorption spectra under the influence of dilute acids and alkalis are indicated. It is necessary to mention Russian methods: 1. Porai-Koshits, based on the photometric measurement of the absorption bands of light reflected from an uncolored and colored fabric (or object). The intensity of maximum absorption by different dyes is very characteristic for them. 2. N. A. Umov's method is based on the characterization, using a Savart polariscope, of the absorption of light rays going into the spectroscope from a colored surface. A spectrum is obtained, cut across the color bands by a bead-like dark line, which is very characteristic in its shape for each dye. The darkest places correspond to the rays most adsorbed by the surface. One can also study solutions. 3. G. P. Voronkov's method is also based on the spectrophotometry of colored fibers in transmitted and reflected light. Comparison of the spectra makes it possible to determine the degree of light absorption by the dye under investigation. Finally, for differentiating mixtures of dyes, Goppelsroeder's capillary method is convenient. A strip of filter paper is immersed 1 cm into a solution of the dye mixture in water or alcohol, having secured its free end on a stand. By virtue of different capillarity, the solutions of different dyes rise to different heights, giving differently colored horizontal bands. The multi-colored strips are cut off and subjected to extraction and analysis by the methods indicated above. Mineral dyes are used mainly for painting buildings and household items, less often for dyeing fabrics and as cosmetic agents, and even less often for coloring food products. Sometimes mineral substances are mixed with organic dyes for the purpose of falsification. Thus, indigo is falsified with Prussian blue, cobalt dyes; natural yellow dyes with salts of iron, chromium. Chalk, gypsum, talc, white clay, asbestos, ultramarine, iron pigments, including Prussian blue, and soot are recognized as harmless mineral dyes. The following belong to poisonous dyes. White: lead white (basic lead carbonate), zinc white (zinc oxide), zinc sulfide with zinc oxide (Lithopone). Red: cinnabar (mercuric sulfide), antimony cinnabar (antimony oxysulfide), realgar (arsenic disulfide), red lead (lead oxide and peroxide), chrome red (basic lead chromate). Green dyes: verdigris (basic copper acetate), Brunswick or mountain green (basic copper carbonate), Bremen green (copper hydroxide with gypsum), Swedish or mineral green (arsenite of copper oxide); Schweinfurt or English, Paris, etc. green (mixture of copper arsenite and acetate), Scheele's green (basic copper arsenite), green cinnabar, Naples green (mixture of lead chromate with Prussian blue), copper borate.

Yellows: zinc (zinc chrome), yellow ultramarine (barium chrome), chrome (chrome yellow, lead chromate), tin sulfide (mosaic gold), litharge (lead oxide), Cassel (lead chloride and zinc oxide), Naples (antimony-lead salt), orpiment (arsenic trisulfide). Blues: mountain blue, copper azure (basic copper carbonate), smalt (potassium and cobaltous oxide silicate, often with an admixture of arsenic). Harmfulness from mineral Dyes is observed upon their entry into the respiratory tract, stomach, onto the skin, or into the eyes. Dyes can be dangerous as in the Leeds Table.

By adding reagents, coloring substances are colored into the following colors. Coloring substances: Annatto, Annatto + pure oil, Turmeric, Turmeric + pure oil, Saffron, Saffron + pure oil, Carrot (carotene), Carrot + pure oil, Marigold juice + pure oil, Safflower yellow, Aniline yellow, Martius yellow, Victoria yellow. Concentrated sulfuric acid: Indigo-blue, turning into violet; Blue, green, turning gradually into violet; Pure violet; Violet to purple; Violet, turning into reddish-brown; Dark blue, quickly turning into reddish-brown; Brown; Reddish-brown to purple; Dark violet-green; Light brown; Yellow; Pale yellow; Partially decolorizes. Concentrated nitric acid: Blue, disappearing upon standing; Decolorizes; Violet; Violet to reddish-violet; Light blue, turning into light reddish-brown; Blue, turning into green and brown; Decolorizes; Yellows and decolorizes; Blue, quickly turning into dirty yellow-green; Colorless; Yellow; Yellow, reddish precipitate; Partially decolorizes.

Sulfuric + nitric acids: Blue, disappearing upon standing; Decolorizes; Violet; Violet to reddish-violet; Light blue, turning into light reddish-brown; Blue, turning into purple; NO₂ is formed and a smell of burnt sugar; Yellow, decolorizes; Green; Colorless; Yellow; Yellow; Partially decolorizes. Concentrated hydrochloric acid: Without change, only becomes weak dirty-yellow or brown; Without change; Violet; Pure violet; Yellow, dirty-yellow; Yellow, becoming dirty-yellow; Does not color; Weakly brown; From green to yellow-green; Without change.

| Yellow precipitate | Color is restored by neutralization with ammonia | Table of Späth. Distinctive reactions of the most important natural organic dyes. Coloring substance: Madder, Sandalwood, Blue sandalwood, Fustic, Fiset wood, Quercitron, Turmeric, Annatto, Catechu, Prepared catechu, Gallnuts, Sumac, Cochineal, Tannin, Lac dye, Cudbear. Aqueous extract: Dirty-red, Does not give, Blue-red, Red-yellow solution, Red solution, Red-yellow solution, Yellow solution, Yellow solution, Cloudy yellow-brown solution, Clear yellow-brown solution, Dirty-yellow color, Dirty-yellow color, Blue-red, Colorless extract, Red extract, Blue-red extract. Aluminum sulfate | calcium chloride and sodium carbonate | Ferric chloride 1:10 |

| Hydrochloric acid 1:10 Note Blue-red coloration Blue-red extract Violet precipitate Violet precipitate Blue-red coloration. Red coloration Red coloration Yellow coloration Transparent red-yellow solution Red-brown precipitate Red-yellow precipitate Red-yellow precipitate Blue-red solution White-yellow precipitate Blue-red solution Blue-red solution Red coloration Red coloration Red-violet solution Yellow solution Red-yellow solution Yellow precipitate Yellow precipitate Yellow solution when doused Yellow coloration Yellow coloration White-yellow coloration Yellow coloration Red coloration White-yellow precipitate Red coloration From aluminum sulfate light-red coloration Dark-brown precipitate Black-brown precipitate Black solution Black precipitate Dark-olive precipitate Dark-green precipitate Yellow precipitate Black precipitate, turning blue with sulfuric acid Dark-green precipitate Light-olive coloration Black-blue precipitate Black precipitate Black coloration Black-blue precipitate Gray precipitate Light-red coloration Red precipitate Red precipitate Red precipitate in strong solution Red precipitate in strong solution Red precipitate Yellow precipitate Yellow precipitate Red precipitate Yellow precipitate Yellow precipitate Turbidity Yellow precipitate Black precipitate Turbidity, Red precipitate in strong solution Red precipitate Red precipitate Yellow-red coloration Yellow-red coloration Light-yellow coloration Light-yellow coloration Light-yellow coloration Red coloration Light-yellow precipitate Light-yellow precipitate Light-yellow precipitate Light-yellow precipitate Light-yellow precipitate Light-yellow precipitate Yellow coloration Yellow coloration Red alcoholic extract, carmine lake Flavii Red cotton in alkaline solution Turns brown when heated with K₂Cr₂O₇ From K.i₇ yellow-brown coloration Orseille conditions of everyday life when using painted objects, as well as in working conditions: during the production of dyes, painting of objects, removal of old paint, etc. The active poisonous principles of mineral dyes are arsenic, antimony, mercury, lead, copper, chromium, barium, uranium, tin, zinc, cadmium; dyes containing them are prohibited for coloring food products in all countries. As for other objects of painting, German legislation makes some exceptions here. Since the German law of 5/VII 1887 has not lost its practical significance to this day, and there is no corresponding law in Soviet legislation yet, it is provided in full. § 1. Dyes harmful to health cannot be used for the preparation of food and flavoring agents intended for sale. Dyes harmful to health in the sense of this definition include those coloring substances and dye mixtures that contain antimony, arsenic, barium, lead, cadmium, chromium, copper, mercury, uranium, zinc, tin, gamboge, corallin, picric acid. § 2. For the storage or packaging of food and flavoring agents intended for sale, vessels, casings, or protective covers prepared with the help of dyes listed in the 2nd paragraph cannot be used. § 1. This definition does not extend to barium sulfate (heavy spar, blanc fixe), barium lake dyes not containing barium carbonate, chromium oxide, copper, tin, zinc and their alloys used as metallic dyes, cinnabar, tin oxide, tin disulfide as imitation gold, as well as to all dyes fired onto glass mass, glazes or enamels, and to dyes covering the outside of vessels made of water-impermeable substances. § 3. For the preparation of cosmetic products (agents for cleansing, preserving, or coloring the skin, hair, and oral cavity) intended for sale, the substances listed in the 2nd paragraph of § 1 cannot be used. This definition does not extend to barium sulfate (heavy spar, blanc fixe), cadmium sulfide, chromium oxide, cinnabar, zinc oxide, tin oxide, zinc sulfide, as well as to copper, tin, zinc, and their alloys in powder form. § 4. For the preparation of toys intended for sale (including pictures, picture books, and watercolor paints for children), flower pot grates, and artificial Christmas trees, the dyes listed in the 2nd paragraph of § 1 must not be used. This definition does not extend to coloring substances listed in § 2 (2nd paragraph), and in addition to antimony pentasulfide and cadmium sulfide as a coloring agent for rubber mass; to lead oxide in varnishes; white lead as a component part of so-called wax casting, but in an amount not exceeding 1 part by weight per 100 parts by weight of wax mass; to lead chromate (separately or in combination with lead sulfate) in the form of oil or varnish paint or, if it is covered with varnish or linseed oil, to water-insoluble zinc compounds: in rubber products, if these compounds are used as coloring agents for rubber mass, in the form of oil or varnish paints or covered with varnish or linseed oil; to all dyes fired onto glaze or enamel. When using substances listed in §§ 7 and 8 for the manufacture of toys, one should be guided exclusively by the provisions of §§ 7 and 8. § 5. For printing and lithographing on objects listed in §§ 2, 3, and 4, only dyes containing arsenic must not be used. § 6. All kinds of dry watercolor paints must not be sold as dyes not containing substances harmful to health or poisonous if they do not meet the requirements of the 1st and 2nd paragraphs of § 4. § 7. For the preparation of wallpaper, furniture fabrics, carpets, curtain fabrics or clothing materials, masks, candles, as well as artificial leaves, flowers, and fruits intended for sale, dyes containing arsenic must not be used. This provision does not extend to mordants or fixing agents containing arsenic for fixing color during the dyeing or printing of yarn and fabrics. But yarns or fabrics treated in this way must not be used for the preparation of the items named in the 1st paragraph if they contain arsenic in a water-soluble form or in such an amount that there is more than 2 mg of arsenic per 100 cm² of the surface of the finished object. The Imperial Chancellor is authorized to issue regulations regarding methods for the quantitative determination of arsenic. § 8. The provisions of § 7 extend to the manufacture of writing supplies, lamp shades, and candles intended for sale, as well as candle collars. The preparation of wafers is subject to the provisions of § 1, although the use of barium sulfate (heavy spar, blanc fixe), chromium oxide, and cinnabar is permitted if they are not intended for internal use. § 9. Water or glue-based dyes containing arsenic must not be used for painting floors, ceilings, walls, doors, drop-down or roll-up blinds or curtains, furniture, and other household items. § 10. The provisions of §§ 2 through 9 do not extend to dyes containing the substances listed in § 1, paragraph 2, not as necessary component parts, but as foreign impurities, and only in amounts inevitable with the methods of paint preparation used in technology. § 11. The provisions of this law do not extend to the dyeing of fur goods. In addition to § 10 of this law, one can also cite the following standards adopted by the Free Union of Bavarian Chemists regarding the tolerable limits of harmful impurities in dyes permitted for use. In 100 g of dye dried at 100° there may be: Impurity Tartar emetic Arsenious acid..... Lead sulfate ....... Lead acetate ..... Lead carbonate ....... Barium chloride ....... Cadmium sulfate ....., !Quantity|! in g 0.51 0.26 0.29 0.29 0.25 1.51 2.16 Impurity :Quantity, I in g Potassium dichromate . . . . Tin dichloride ....... Copper sulfate ....... Cobalt sulfate ..... Nickel sulfate ...... Uranium acetate ..... 0.56 1.60 0.45 2.63 2.63 2.47 Russian pre-revolutionary legislation, by the announcement of the Medical Council of 28/VI 1868 in the Collection of Legalizations and Government Orders, indicated only the technical names of harmful and harmless dyes without defining exceptions in the spirit of the German law. Soviet legislation, as indicated above, by a circular of the People's Commissariat of Health of the RSFSR, along with the prohibition of coal-tar dyes in the food industry, completely prohibited mineral dyes as well, with the exception of ultramarine. The determination of mineral dyes is carried out according to the general rules of mineral analysis with special attention paid to lead, arsenic, mercury, chromium, and antimony. Preliminary preparation of the material consists of scraping the dye from the object and dissolving it in nitric acid. It is often necessary to destroy the organic matter that accompanies the dye. Direct ashing is risky here due to the possibility of losing volatile compounds of Hg, As, Cu, Zn, Pb.

The best method is the destruction of the substance with chlorine by mixing HCl with KClO₃ (according to Fresenius-Babó) or with a mixture of equal parts of H₂SO₄ (sp. gr. 1.84) and HNO₃ (sp. gr. 1.4) while heating (according to Neumann and Werner). The casuistry of poisoning by mineral dyes in domestic settings is quite rich. According to Erisman, poisonings were observed from wearing colored fabrics containing lead and especially antimony. According to Khlopin, stockings dyed red with antimony dye were more than once the cause of eczema. According to Lehmann, Schweinfurt green, a beautiful green dye containing As and Cu, sometimes used for coloring lampshades and fabrics, despite its durability, can cause serious poisoning. From wallpaper colored with arsenic-containing dye, under the influence of molds, a highly poisonous arsenic hydride with a garlic odor is released into the air. Mörner confirmed the release of mercury into the air by wallpaper. Bulowski found lead and zinc in silk rubber nipples, and antimony in reddish-brown ones, and confirmed the transfer of the first two into saliva. In rubber toys colored on the surface, he encountered lead in white dyes, umber in light brown ones, French green and green cinnabar (a mixture of lead chromate with Prussian blue) in green ones, and ultramarine (capable of releasing H₂S under the influence of stomach HCl) in blue ones, cinnabar in red ones, and lead chromate in yellow ones. The coloring of food products with dangerous mineral dyes relates mainly to copper salts (CuSO₄), which give a fresh appearance to canned vegetables and fruits and preserve the freshness of flour. Millet is colored with yellow lead dyes, and tea and rice are colored with smalt, ultramarine, and Prussian blue. In confectionery products, harmful mineral dyes of all colors were often found.

Dyes in bacteriology and chemotherapy. In bacteriology, various dyes are used (fuchsin, methylene blue, eosin, safranin, methyl violet, malachite green, etc.)—some for staining bacteria in a preparation, others as indicators when growing various bacteria, since they change their color under the influence of acids or alkalis formed; still others (e.g., fuchsin or malachite green) are reduced, converted into leuco-compounds, and added to nutrient media, where, under the influence of the oxidative capacity of certain microbes, they turn back into dye (Endo, Padlewski media). In addition, dyes are added to inhibit the growth of certain bacteria and thus facilitate the isolation of others from a mixture. Methyl violet (Pyoctaninum coeruleum) and auramine (Pyoctaninum aureum) are used as antibacterial agents; for the same purpose, Brilliantgrün is used for treating purulent wounds, exceeding the antiseptic power of mercuric chloride by 20 times. Finally, when using dyes for intravital staining, it was discovered that dyes containing certain groups possess an affinity for specific tissues; for example, dyes containing a sulfur atom, as Ehrlich showed, possess the property of staining only the nervous system. Such dyes are methylene blue, thionine, methylene azure; Bindschedler's green, which differs from methylene blue only by the absence of S, does not stain nerves but stains the heart muscle. These neurotropic properties of methylene blue led Ehrlich to the idea of using it as a medicinal agent. It is now used as an analgesic and pyrogenic agent. The intense staining of the malaria plasmodium by this same dye gave reason to use it for the treatment of this disease, and its effect on the parasite f. quartanae is identical to the effect of quinine. Furthermore, Ehrlich showed that there are monotropic dyes, i.e., those that stain only one tissue, and that the majority of dyes are polytropic, but nevertheless, they stain one tissue more strongly. It is well known that certain dyes selectively stain specific microbes. Such a property (monotropism) allowed Ehrlich to use parasitotropic dyes, i.e., those that are fixed by the microorganism and do not affect the host's tissues. The entire field of chemotherapy rests on this fact. The first dye used for chemotherapy (Ehrlich, 1904) was trypan blue and trypan red. These works gave impetus to a long series of analogous studies, and in 1906, Nicolle and Mesnil introduced into therapy violet Afridol, a combination of diamino-diphenyl-urea with amino-naphthol-sulfonic acid, a compound close to 'Bayer 205'. Further, it became clear that a chemotherapeutic substance may not be a dye, but it must contain a group analogous to a chromophoric one, which here is called a toxophoric group and which is fixed by the chemoreceptor groups of the microbe thanks to NH₂ and OH receptors (in dyes—auxochromes). Ehrlich illustrates this in relation to salvarsan as follows: salvarsan is diamido-dioxy-arsenobenzene NH₂-C₆H₃(OH)-As-As-C₆H₃(OH)-NH₂, where -As-As- is the toxophoric group, and the NH₂ and OH groups are haptophores (see above amido-azo-benzene, where -N=N- is the chromophoric group, and NH₂ is the auxochromic group). The entire compound is a chemotherapeutic agent in the form of a poisoned arrow, where the toxophore is the poison with which the tip of the arrow is impregnated, the haptophores are the tip of the arrow, and the benzene nuclei, the carrier of the haptophores and toxophores, are the shaft of the arrow. By introducing various toxophoric and haptophoric groups into the compound and changing the position of the latter, one can change (similar to how it is done in dyes) the toxic effect of the preparation and its selective action. This fact allows us to consider chemotherapeutic substances from a chemical standpoint as dyes, but dyes with a specific affinity for a specific type of microbe.

A. Savateev, V. Uglov. Professional hazards in the production of dyes. Inorganic dyes are manufactured from various natural coloring substances found in nature in the form of various kinds of minerals and ores (iron, lead, copper, zinc, chromium, manganese, arsenic, antimony, cadmium, tin, cobalt, etc.), or from other substances (non-coloring) by artificial means. To obtain natural mineral dyes, natural coloring substances undergo special processing, whereby these substances are usually subjected to grinding, sifting, levigation, sometimes calcination, and finally drying. When obtaining dyes by artificial means, the starting materials or raw materials used for this are subjected beforehand to a series of chemical operations leading to the formation of the coloring substance itself, after which the obtained product is again ground, washed, and dried. Mineral dyes are used mainly in painting, wallpaper production, and house painting. In the textile industry, for dyeing products made of fibrous substances, organic dyes predominate, while inorganic dyes are used rarely and in very limited quantities. The basic technical properties that distinguish one dye from another are 1) coloring power, 2) intensity of dyeing, 3) stability and durability in relation to various external influences (sunlight, air, moisture, acids, alkalis, etc.). Most mineral dyes are poisonous, and they pose a danger if handled carelessly not only in the process of their production but also when used in their finished form in painting, house painting, in the dyeing of wallpaper, fabrics, paper, etc. For the processing of materials used in the production of dyes, the following types of apparatus and machines are used in factories: 1) wooden vats with manual or mechanical stirrers for obtaining solutions and washing dyes; 2) filters in the form of hair sieves or wooden frames of various shapes with canvas or linen fabric stretched over them for obtaining precipitates and cleaning auxiliary products and materials from foreign impurities; 3) crushers, sifters, edge runners, ball or cone mills for crushing and grinding masses; 4) drying apparatus of various types and systems; 5) paint-grinding machines, serving to form a fine mixture of coloring and binding substances (oil, varnish, etc.). In the production of mineral dyes, the use of the aforementioned open apparatus, which is also, in most cases, devoid of suction devices, leads to the formation of dust and vapors during work, which are the main factors in the contamination of the air in work premises with various harmful and poisonous substances. These factors acquire particular importance during the production of dyes from poisonous materials (lead, arsenic, chromium, mercury, etc.). Dyes of various colors produced from lead have gained the greatest distribution and, at the same time, professional-hygienic significance; these include: white (lead white), red (red lead), yellow (litharge, massicot, and chrome yellow), mixed greens, etc. The production of lead dyes, especially white lead, is one of the most harmful industries. Of all the methods for obtaining white lead [2 PbCO₃·Pb(OH)₂]—Dutch, German, and French—undoubted preference from a professional-hygienic point of view should be given to the French wet-precipitation method, based on obtaining white lead by precipitating it with carbonic acid from a solution of lead litharge in acetic acid. This method, improved in the USSR by Professor Shpitalsky, makes it possible to conduct the entire process of white lead production in a wet state in closed and sufficiently mechanized apparatus, which should lead to a significant improvement in the health conditions of this production. The methods for obtaining white lead by the dry method, used until now both in the USSR and abroad, result in a large number of lead poisonings (see Lead), significantly exceeding the incidence rate of other lead-related professions. The production of other lead dyes, such as litharge (PbO) and red lead (Pb₃O₄), is carried out in special furnaces by calcining metallic lead with access to air. Until recently, the stirring of lead in furnaces at some factories, both ours and foreign (Germany), was performed manually with the help of long and very heavy iron scrapers. This work causes extremely strong muscle strain in workers, which, in the presence of lead vapors and dust in the air of the room, significantly increases the risk of lead poisoning. In Germany, all furnaces of the latest construction, according to the regulations existing there, must have mechanical devices for feeding lead into them, stirring it, and unloading it. In the USSR, the construction of mechanized factories for the production of litharge and red lead is currently being completed, which will lead in the near future to the cessation of the use of old-style furnaces. In a number of states (Austria, England, Belgium, Germany, the Netherlands, France, Norway, Switzerland, etc.), laws have been issued for the protection of persons working in the production of lead dyes. The basic rules of these regulations require the removal or destruction of lead dust, the prohibition of the work of women and children, periodic medical examinations, and personal and general hygienic measures. The mandatory decree of the People's Commissariat of Labor of the USSR of October 11, 1924, "On the structure and maintenance of enterprises producing lead dyes and other lead compounds" and the decree of the People's Commissariat of Labor of the USSR of August 16, 1929, "On the manufacture, sale, and use of white lead" also provide for all necessary measures to protect the workers of these industries from the hazards of their work. Mandatory monthly periodic examinations of workers employed in the production of white lead, lead acetate, lead chromate, red lead, and lead litharge were established by the decree of the People's Commissariat of Labor and the People's Commissariat of Health of the RSFSR of September 24, 1925. Among other white dyes that have recently acquired particularly great importance, zinc white (ZnO) should be noted. Due to their good technical qualities (whiteness, covering power, resistance to external influences), these whites have begun to be widely used as dyes replacing white lead, and in many painting works, they have almost completely supplanted lead dyes. The production of zinc white is associated with the presence of workers near strongly heated furnaces (having an internal temperature of 800–1,000°), which very intensely radiate thermal energy, as a result of which the workers serving these furnaces (furnace operators, muffle operators) have to be exposed to high temperatures (43–51°) during a whole series of operations—charging zinc into retorts, poking retorts, changing them, loading and unloading white from muffle furnaces, and some other work processes. In other production processes associated with knocking white out of cone receivers into tubs, tamping them into boxes, and packaging, a significant amount of dust is released, which enters the air of the work premises. Other hazards of zinc-white production are associated with the formation of vapors of lead and cadmium, which are part of the impurities contaminating the zinc used for the production of white. Lead oxide is also contained in finished zinc dyes. All this does not exclude the possibility of the appearance of cases of lead poisoning at zinc-white factories. In rare cases, illnesses of workers with metal fume fever are also possible. Health measures in this industry should be aimed at eliminating the influence of high temperature and radiant energy on workers, at the mechanization of work associated with feeding, loading retorts into furnaces, and unloading them, and at dedusting work premises. In some countries (e.g., Germany), the sale of zinc white with a lead content of more than 2% is prohibited. In the very recent past, abroad (Norway, USA), so-called titanium white has begun to be produced in large quantities, which is not inferior in its technical qualities to lead dyes and is, according to some data (Schoofs and Lehmann), inert from a physiological point of view and devoid of poisonous properties. A less valuable white dye capable of replacing white lead only for interior painting is lithopone—a mixture of zinc sulfide and barium sulfate (BaSO₄ + ZnS), which contains absolutely no lead. Preventive measures for combating hazards in the production of arsenic dyes are the mechanization of production processes and the complete replacement of dry methods of dye production with wet ones. In the event of unavoidable contact with arsenic, the hands of workers must be protected with rubber gloves, and the respiratory tract with the wearing of respirators. Flawless cleanliness of the skin and clothing is of great importance in the prevention of arsenic poisoning. In England, Australia, France, and the Netherlands, special mandatory regulations have been issued on the protection of the labor of persons working with arsenic.

By a mandatory decree of the People's Commissariat of Labor of the USSR dated September 19, 1924, the use of arsenic in the coloring of any objects whatsoever is prohibited. In the process of manufacturing chrome dyes, during the evaporation of chromate solutions, and especially during the drying of crystalline chrome compounds, chrome dust forms in the workrooms, reaching, according to Lehmann, 0.1–0.5 mg per 1 m³ of air, and according to Fischer, 0.1–37.2 mg. The use of production processes that completely prevent the formation of chrome dust, the impermeability of mechanisms used for grinding raw materials and finished products, and the installation of rational ventilation—these are the basic measures that must be applied for the purpose of improving the health conditions of this production. Among personal preventive measures, all those rules of personal hygiene that are mandatory when working with other similar poisonous substances are applicable here [respirators, impermeable gloves, rubbing the face and hands with Vaseline or greasing them with a special protective ointment (Oppenheim), rational work clothing, washing the body]. In some European countries, special decrees have been issued (in Germany, the law of May 16, 1907) concerning the setup and operation of enterprises for the production of alkaline chromates. In the USSR, the People's Commissariat of Labor issued (April 10, 1922) a special decree on safety measures in the production of chrome salts; workers employed in this production are subject to mandatory periodic medical examinations (decree of the People's Commissariat of Labor and the People's Commissariat of Health dated September 24, 1925). Among mercury dyes, red cinnabar (mercury sulfide - HgS) is of primary importance. This dye is used mainly in painting. Due to its high cost, it has not become particularly widespread. The preparation of mercury cinnabar as a red dye is carried out mainly by artificial means, and the natural mineral cinnabar, which is considered insoluble and harmless and is used almost exclusively for the production of mercury, is very rarely used for this purpose. In the artificial production of cinnabar, mercury is mixed directly with sulfur, whereby in the dry production method dust is formed during the work process, and in the wet method, due to the heating of mercury compounds, a large amount of mercury vapor is formed. Work in the production of mercury dyes under these conditions is associated with the danger of the occurrence of mercury poisoning (see Mercury) in persons employed in this production. The phenomena of mercury diseases discovered in workers at mercury dye factories were not inferior in their severity to the symptoms of poisoning observed in workers of other mercury industries (Legge). For the purpose of possible improvement of working conditions in the production of mercury dyes, it is necessary, in all processes of mercury vapor sublimation, as well as in dusty work (mixing and sifting), to use exclusively hermetically sealed equipment equipped with properly constructed exhaust hoods. Special attention should be paid to preventing the spilling of mercury, and work should, if possible, be carried out in rooms with a low temperature in order to minimize the evaporation of mercury. It is also extremely important that workers strictly observe all the personal hygiene rules listed above. In addition to the poisonous dyes described, a special mineral dye of blue color with various shades—ultramarine—which currently has extensive application in industry, is of certain interest from a professional-hygienic point of view. This dye is used in the cotton, wallpaper, soap, sugar, and other industries. The composition of ultramarine includes kaolin, infusorial earth, soda ash, and tar. The manufacture of ultramarine boils down to the following operations: mixing and grinding its constituent parts in mills, roasting the resulting mixture in special furnaces at a temperature of 900°, washing, elutriation, drying, and sifting the finished product. The main professional hazards encountered in this production consist of the following. 1. High temperature in various departments, reaching 62–64° in some operations (removing pots from furnaces) and even 70° (unloading the dryer, raw materials). 2. The release of a significant amount of very fine and light ultramarine dust in most workrooms. The concentration of dust in the air fluctuates within the range of 466 mg to 1,176 mg per 1 m³ of air (in the sifting department). Ultramarine dust, under the influence of acids, decomposes with the release of hydrogen sulfide. This phenomenon explains the unpleasant and painful eructation of rotten eggs observed in many workers, the decrease in the acidity of gastric juice, and the almost complete lack of appetite. Upon the penetration of ultramarine dust into the lungs and its deposition in the alveolar tissue, the formation of ultramarine pneumoconiosis is possible. Health improvement measures in this production should consist of the following: 1) complete dust removal from all production processes; 2) rationalization of the work regime during operations taking place in conditions of high temperature (short work intervals with rest periods); 3) combating high temperature and increased humidity by installing ventilation; 4) mechanization of a number of production processes (sifting the composition, crushing, and packaging of ultramarine). As for all other mineral and earth dyes (iron, copper, manganese, cobalt, tin, ochre, mummy, etc.), in view of the fact that some of them have not received particularly wide distribution in the dye industry, while others are comparatively harmless (earth dyes), they do not present particularly great interest from a professional-hygienic point of view. D. Kagan. Organic dyes. The basic starting substances for obtaining artificial organic dyes are products of coal tar distillation. During the fractional distillation of this tar, a number of aromatic hydrocarbons are obtained, which, depending on the temperature at which the distillation is performed, are divided into 4 groups: light oils (up to 170°), medium oils (up to 230°), heavy oils (up to 270°), and anthracene oils. By further fractional distillation of these oils, the basic starting products are obtained: benzene, toluene, xylene, naphthalene, cresol, anthracene, etc., from which, by further processing, a number of intermediates are obtained, among which, besides benzene, its nitro- and amido-derivatives are of the greatest importance: nitro- and dinitrobenzene, aniline, paranitraniline, toluidine, dinitrochlorobenzene, phenols, naphthols, and many others. The production of artificial organic dyes, which originally arose in England, moved from there to France and subsequently reached particularly strong development in Switzerland and Germany. In the latter, this production represents an extremely important branch of industry, in which over 200,000 workers were employed even before the war. In Russia, until 1914, almost all complex dyes were imported from Germany. This production arose in Russia during the imperialist war, when the first few factories were built; in the post-revolutionary period, it began to develop rapidly, and at the present time in the USSR there is a decent network of factories of the coke-benzene and aniline industry, where intermediates and finished dyes are produced; the number of workers at these factories already reaches tens of thousands. The production of intermediates and finished dyes should be considered particularly dangerous and harmful. Very many intermediates are in themselves strong poisons; during the manufacture of finished dyes from them, the most diverse gaseous and vaporous emissions are released, which very often represent poisons, sometimes not yet fully studied. In view of the extremely large number of the most diverse processes taking place during the manufacture of coal-tar dyes, and the professional hazards associated with them, we provide a brief list of only the main chemical operations and a characterization of the production of the most important groups of dyes from the point of view of professional hygiene. Main operations. 1. Sulfonation—treatment with strong sulfuric acid for the purpose of replacing an H atom with an SO₂.OH group. Hazards: manipulation with products subject to sulfonation (benzene, aniline, toluidine), release of sulfurous gas. 2. Fusion with caustic alkali for the purpose of replacing the sulfonic group with a hydroxyl group. 3. Nitration—treatment with nitric acid; one of the most frequent and, moreover, most harmful processes, associated with the release of nitrogen oxides into the air. 4. Reduction is performed with the help of HCl and iron filings. 5. Chlorination—introduction of a chlorine atom; accompanied by the release of hydrogen chloride and chlorine. 6. Alkylation—introduction of a methyl or ethyl group (dimethyl sulfate is especially dangerous). 7. Oxidation. 8. Carboxylation (introduction of a COOH group). 9. Diazotization—introduction of a diazo group, which is performed by treatment with nitrite (see Azo dyes). This process is one of the most frequent and, moreover, quite harmful. Most important productions. 1. Production of aniline (see Aniline). 2. Production of paranitraniline. The process consists of the formation of acetanilide from aniline and strong acetic acid, which upon nitration turns into nitracetanilide; the latter, as a result of treatment with caustic soda, turns into paranitraniline.

Main hazards: contact with aniline during its non-mechanized loading, the release of nitrogen oxides during nitration and (most importantly) the release of paranitraniline dust during its unloading from dryers, grinding, and filling into barrels. During the latter processes, acute and subacute poisonings of workers occur quite often. The effect of paranitraniline on the body is similar to that of aniline; anemia is more sharply pronounced. Paranitraniline serves as the main component for obtaining the richest and most common group of diazo dyes. If the basic condition—maintaining the necessary temperature (0°) during the reaction of coupling diazo salts with amines—is not observed, nitrogen oxides are released into the air, due to which poisonings of workers occur both at aniline plants and at calico printing factories. 3. Production of nigrosine for dyeing leather, which is obtained by the interaction of aniline, nitrobenzene, and hydrochloric acid in the presence of cast-iron shavings; these intermediate products are fused at a high temperature in tightly closed boilers under pressure. The main hazard of this production consists in the release of aniline vapors during the extraction (removal) of the hot mass of nigrosine from the boilers, and it is during this that poisonings most often occur (at the Moscow Butyrsky plant, 7 cases of poisoning occurred within 3 months). 4. Production of sulfur Dyes. The latter are obtained as a result of the action of various aromatic compounds on polysulfides (formed from the action of sulfur on a solution of sodium sulfide): for example, sulfur black is obtained by the interaction of polysulfides and sodium dinitrophenolate; sulfur blue—by the interaction of polysulfides and indophenol (the latter is obtained by the interaction of orthotoluidine, sulfuric acid, and nitrosophenol), etc. A general hazard in the production of all sulfur dyes is the release of large quantities of hydrogen sulfide, which occurs during the boiling of sodium sulfide, when adding sulfur to the boilers, during the cooking of dyes, during the unloading of finished dyes, and in subsequent processes of filtration and precipitation of the finished dye. In these jobs, there have been cases of acute poisoning of workers with H₂S. Dinitrochlorobenzene and nitrosophenol, which are part of these Dyes, possess a caustic, irritating effect on the skin; contact with the skin, especially sweaty skin, of even the smallest amounts of these substances causes severe eczema and incapacitates workers for long periods (see Dinitrochlorobenzene). During the processes of grinding, mixing, and packing finished dry dyes into containers, large amounts of fine dust are released, very often possessing poisonous and irritating properties. In workers employed in these jobs, an increased number of skin diseases is noted. For example, Bachfeld registered 159 cases of serious skin lesions among 4,945 workers at the Offenbach aniline plant over 6 years: inflammatory processes, eczema, increased sweating of the hands (from washing with soda, chlorinated lime, sodium hyposulfite), etc. The contact of workers with the most diverse poisonous substances, the release into the air of various poisonous gases, vapors, and dust create conditions under which numerous acute, subacute, and chronic poisonings of workers arise. In Germany, in the first years of the emergence of the aniline industry, when production was still at a low stage of development, processes were not sufficiently mechanized, were carried out outside of fully enclosed apparatus, and the number of both acute and chronic poisonings among workers was quite large; numerous reports in the literature speak of this (Curschmann, Rambousek, Bachfeld, Grot, Kölsch, etc.). Of particular interest in Germany and Switzerland was the report by the surgeon Rehn, subsequently confirmed by further observations, on the development of malignant neoplasms of the bladder in workers in the aniline industry (Rehn, Schwerin, Nassauer, Oppenheimer, Leienberger, etc.). In connection with the campaign raised in the press regarding this report, fundamental changes were made in the dye industry of Germany and Switzerland in terms of sealing and mechanizing apparatus, installing ventilation, and generally reorganizing plants with the introduction of numerous sanitary-hygienic devices (washbasins, changing rooms, showers, canteens, etc.). As a result of these measures (the first decade of the 20th century), the number of poisonings indeed fell significantly. A new outbreak was caused by the imperialist war, during which most enterprises were converted to the production of explosives. As a result of the lengthening of the working day, the introduction of a large number of unskilled labor and women, the deterioration of working conditions, and work with new, highly poisonous substances, the number of occupational diseases and poisonings rose sharply (Grot, Kölsch, etc.). In those same years, numerous cases of toxic jaundice occurred at these enterprises due to the influence of trinitrotoluene or its impurities (Kölsch). In the postwar years, the number of diseases and poisonings fell again, but nevertheless, cases of acute poisoning are registered quite often (reports by Curschmann, Floret, Kölsch, etc.). At USSR plants, where production is still in a state of development, many processes are not yet sufficiently sealed and mechanized, and where new productions are being introduced, the danger of which has not yet been fully studied, cases of acute poisoning of workers in the production of organic Dyes are observed quite often. Serious attention is paid to the protection of workers' labor in the production of organic dyes in the USSR. A significant number of poisonings, as a rule, relates to the first periods of operation of new productions. As the hazards of production are identified and studied (which the sanitary inspection and scientific research institutes are intensively engaged in), appropriate measures are taken to eliminate them, and poisonings are eliminated completely or become a rare exception. General measures for improving labor in this branch of industry are, first and foremost, the full mechanization of production in all its stages of main and auxiliary work (the latter includes repairs and cleaning of apparatus), the sealing of apparatus and careful monitoring of its actual impermeability and serviceability, the installation of rational ventilation with exhaust ventilation structurally connected to the apparatus to create a vacuum in the apparatus and with the supply of an excessive amount of fresh air to the work premises. If it is impossible to introduce full mechanization and sealing of the apparatus, it is necessary to implement special safe labor regimes and provide workers with individual protective equipment and rational special clothing developed for each production. As examples of achievements in this area, one can point to the following: in the production of nigrosine, after the introduction of gas mask helmets with a supply of fresh air during the extraction of the finished product, acute poisonings of those working during this operation ceased completely; after the mechanization of aniline supply to the apparatus using pumps through closed pipes, the previously occurring poisonings of workers from aniline wetting the skin and clothing ceased; after replacing the process of removing dinitrochlorobenzene from barrels by hand with melting it out in closed chambers with steam, mass skin diseases ceased, etc. In this production, as in poisonous productions in general, the professional selection of workers and subsequent periodic control over the state of their health, thorough technical training and sanitary education of workers, and the arrangement of auxiliary premises—washbasins, showers, changing rooms, canteens, etc.—are of extremely great importance. S. Kosourov, N. Rozenbaum.

[General] technology of fibrous and coloring substances, VI.—Kiev, 1926; Agasse-Lafont E., Industrie de la peinture (Hygiene du travail, Encyclopedic, fasc. 58, Geneve, 1926); Fleck A., Die Berufskrankheiten der Maler, Diss., B., 1915; Fühner H., Die Gruppe der organischen Farbstoffe (Hndb. d. exp. Pharmakologie, hrsg. v. Heffter, B. I, B., 1923); Weyls Handbuch der Hygiene, B. III, Lpz., 1913 and B. VII, T. 2, Lpz., 1921.