POISONS

POISONS (Lat. venena). In ordinary speech, P. are generally understood as substances that, through their chemical action, can cause disease and death of the organism. In this sense, one speaks of poisonous and non-poisonous substances. However, such a division cannot be strictly drawn. Sodium chloride, a normal component of all animal tissues and food, when it comes into contact with the nasal mucosa, can cause ulcers here and even perforation of the cartilaginous part of the nasal septum. Nitrogen, which would seem to be physiologically completely indifferent, caused anesthesia in frogs at a pressure of 90 atm. Breathing pure oxygen at a pressure of 4 atm. leads to the rapid death of a warm-blooded animal. On the other hand, many substances, known for certain as P., are in small quantities normal components of blood and tissues: the best-known household P.-ethyl alcohol-is normally present in human blood (when examined on an empty stomach) in amounts of 2.4-6 mg%; hydrochloric acid is a normal and completely necessary component of gastric juice; fluorine compounds are a frequent cause of poisoning, yet healthy people's blood contains a significant amount of fluorine-0.2-0.3 mg%. As the sensitivity and accuracy of chemical methods for quantitative determination of poisons in blood and tissues increase, it becomes increasingly clear that even substances such as lead (in some Mexican Indians living in almost primitive conditions, 0.01 to 0.06 mg% was found in the blood), mercury, arsenic, carbon monoxide, and many others are present in the normal human body. It is also difficult to distinguish between P. and medicinal substances, since the same substance in small doses can be used for therapeutic purposes, while in large doses it can be a strong P. (see Medicinal Substances and Doses). Of the existing definitions of P., the most appropriate one was given by Starkenstein: "Poisons are exogenous or endogenous substances acting chemically or physico-chemically, which for the entire organism or for a particular organ are foreign in terms of quality, quantity, or concentration, and which therefore cause functional disorders in the living organism." According to this definition, for example, nitrogen or carbon dioxide can become P. if their concentration in tissues increases much above normal. Hydrochloric acid can be poisonous even in the concentration in which it is normally present in gastric juice, if it is introduced into any other organ. It will also be a P. for the stomach if it enters it in much larger quantities and concentrations than under physiological conditions. Starkenstein adds that a substance can be called a P. only when it causes changes in the functions of organs that lie outside the physiological limits of variability of these functions. Therefore, one should not call, for example, lactic acid, which forms in unusual quantities in muscles during heavy physical work and undoubtedly causes certain functional disorders in the body, a P. The number of P. is infinitely large; practically it is limited by the fact that many substances can have a toxic effect only under artificially created experimental conditions that are unusual and not encountered in life. P. can be substances entering the body from outside (exogenous P.) or formed in the body itself, for example, in metabolic disorders, in damage to excretory organs; hormones can also play the role of P. when they are formed in the body in unusual quantities, etc. (endogenous P.). According to their origin, P. are distinguished as mineral, vegetable (e.g., alkaloids, glycosides, saponins), and animal. Previously, the term "organized P." was also encountered; here reference was made to P. of bacterial origin, closely associated with the bodies of bacteria and released upon their destruction. Depending on the conditions in which the harmful effect of P. can occur, one also speaks of household P. (for example, carbon monoxide, alcohol, nicotine, etc.), food P. (see Food Infections, Poisonings), industrial P. (see Industrial Poisons). There is still no single and generally accepted classification of P. according to their action that covers all types of P. action. One can distinguish (according to the place where the interaction between P. and living tissue occurs) P. with predominantly local action (interaction occurs at the place where P. enters the body before absorption into the blood) and P. with predominantly resorptive or general action (interaction occurs in various tissues and organs where P. enter after their absorption into the blood). The first group includes P. that act irritantly (see Irritant substances), cauterizing, or inflammatorily at the site of their introduction. As a result of the local action of poisons, various general disorders in the organism can subsequently occur reflexively, then due to the formation of toxic products of tissue decomposition (e.g., in chemical burns of the skin or toxic pulmonary edema), loss of function of a given organ, etc. The local action of poisons can be directed mainly at certain elements of a given tissue, capillaries (dionin), sensitive nerve endings (pepper, veratrine), directly at cells (cellular P., e.g., cantharidin) or at all or some of them simultaneously (for example, mustard oil). P. with predominantly resorptive action can affect all cells of the animal organism and generally all living things (protoplasmic P., e.g., many heavy metals; also narcotics, which cause in the cell, unlike the former, reversible changes) or act more or less selectively (electively) on certain tissues of an organ or system. In the latter case, one speaks of blood P. (this includes P. acting on hematopoietic organs, e.g., benzene; P. acting on the coloring substance of the blood, including P. causing methemoglobin formation, e.g., chlorate salts, aromatic amino- and nitro compounds; hemolytic P.), parenchymatous P. (causing degenerative changes in parenchymatous organs-liver, kidneys, etc.; these include, for example, phosphorus, chlorinated hydrocarbons, etc.), nerve P., among which several subgroups can be distinguished (e.g., vegetative P., in particular sympathico- and parasympathomimetic, which act excitably on the end apparatuses of sympathetic or parasympathetic nerve fibers and thus cause an effect similar to that obtained by electrical stimulation of the corresponding nerves), etc. There are also special classifications of poisonous gases and vapors, although none of them is generally accepted. Henderson and Haggard distinguish 4 groups of gases: 1. Asphyxiating, which cause suffocation as a result of either a decrease in the partial pressure of oxygen in the lungs (simple asphyxiating-physiologically inert gases, e.g., nitrogen) or (chemically asphyxiating) their binding to the blood's hemoglobin (carbon monoxide) or inhibition of tissue respiration (hydrogen cyanide). 2. Irritating with predominantly local action on the respiratory tract (chlorine, ammonia, etc.). 3. Volatile narcotics and similar substances. 4. Inorganic and metallo-organic gases. For other classifications-see also Combat Chemical Agents. P. can penetrate the body by various routes. Poisonings very often occur through the mouth; absorption of P. can occur in all parts of the gastrointestinal tract: in the mouth (here, for example, cyanides, nicotine, etc. are quickly absorbed), in the stomach (in an acidic environment, some P. can be broken down before absorption and sometimes give more poisonous products; for example, from ultramarine, hydrogen sulfide is formed), but mainly in the intestine. The rate of absorption in the intestine of different P., sometimes even chemically very similar ones, is very different (orthotricresyl phosphate is absorbed well, its meta- and para isomers are almost not absorbed); the rate of absorption of the same substance depends on the filling of the intestine, the type of food (a well-known example is slower absorption of alcohol in the presence of fats) and a number of other factors. Gaseous and vaporous P., as well as P. in the form of dusts, mists, and fumes, penetrate the body mainly through the respiratory tract. Gases that are well soluble in water and strongly chemically active are absorbed mainly in the upper respiratory tract (ammonia, halogen hydrides, etc.); other gases and vapors-in the deep respiratory tract, and mainly in the alveoli. P. in the form of dust with particle size not exceeding 5-10 μ are absorbed mainly in the alveoli; larger particles do not penetrate into the alveoli but are retained in the respiratory tract, first in the upper ones, and are partly absorbed here, partly swallowed with sputum into the stomach. Through intact skin, P.-electrolytes penetrate the body only in rare cases and in small quantities, mainly when rubbed into the skin (mercury); many lipid-soluble non-electrolytes easily pass through the skin, especially those whose solubility in water is not too small (e.g., aromatic amino- and nitro compounds). Intentional and medicinal poisonings can occur as a result of introducing P. into the subcutaneous tissue, into the muscles (and sometimes into other tissues, e.g., when using poisoned weapons), intravenously, etc.

Poisonings are known to occur due to the absorption of Poisons from the vagina (mercuric chloride), the bladder, and also through the conjunctiva of the eyes. It is important to distinguish between enteral and parenteral administration of Poisons; in the latter case, Poisons enter the general bloodstream, bypassing the liver, which plays an important role in the processes of their detoxification. Poisons absorbed from the rectus are also carried by blood bypassing the liver (through plexus haemorrhoidalis and v. iliaca interna). Poisons can undergo rapid transformation at the site of absorption; as a result of this transformation, substances may be formed that are normal components of the organism and moreover in quantities that do not significantly change their concentration in the body; for example, hydrochloric acid when inhaled is probably neutralized already on the mucous membranes of the respiratory tract. In other cases, the transformations proceed more slowly or also yield toxic products. Absorbed Poisons are carried by blood throughout the body and are distributed among organs sometimes in certain fairly constant ratios for a given Poison: for example, concentrations of narcotics in most organs are close to those in the blood and only in certain organs, in particular in the central nervous system, in adipose tissue, can be significantly higher. In this case, the found content of poisons in the blood makes it possible to judge their concentration in organs: blood is as it were a 'mirror' of tissues. Such distribution of narcotics between organs depending on the ability of the latter to bind these Poisons (static distribution) requires a certain time; before such equilibrium is reached, the content of narcotics will be high in organs with good blood supply (nervous system, liver, kidneys, glands) and low in poorly supplied ones (skeleton, muscles at rest, etc.—dynamic distribution). Quite different types of distribution of Poisons can also be observed: Poisons can rapidly disappear from the blood and be distributed among organs very unevenly; their content can be very high in some organs, very low in others (e.g. in the nervous system). Many Poison-electrolytes, in particular heavy metals (lead, mercury, manganese, etc.), are distributed according to this type. In some organs (e.g. bones, liver) such Poisons can be retained for a long time, forming depots from which under certain conditions they can again enter the blood and cause relapses of poisonings. Thus lead, manganese, fluorine, etc. are deposited in bones in large quantities. A frequent case of transformations of Poisons in the organism is their oxidation—for example, nitrites into nitrates, arsenious compounds into arsenates, cyanides partially into cyanates. Reduction occurs less frequently (e.g. nitrates into nitrites, sulfur into hydrogen sulfide), hydrolysis (for example of halogen acid anhydrides), deamination (from benzylamine benzyl alcohol is formed). Poisons can also enter into synthetic processes, in particular forming conjugated compounds with sulfuric and glucuronic acids, with amino acids (in mammals mainly with glycine, in birds with ornithine). The formation of compounds of Poisons with sulfur (conversion of cyanides into thiocyanates), methylation (formation of methylpyridine from pyridine, trigonelline from nicotinic acid), and even more rarely demethylation is also known. The excretion of volatile Poisons occurs mainly through the lungs in those cases when these gases and vapors have low solubility in water and blood (carbon monoxide, gasoline, benzene, ether, etc.). Well-soluble Poisons are most often excreted through the kidneys; poorly soluble non-volatile Poisons—to a large extent through the intestine (heavy metals, among other Poisons also some alkaloids, e.g. morphine) and bile ducts. The salivary (mercury) and sweat glands play a secondary role in the excretion of poisons. Some Poisons can also be excreted through the mammary glands: all lipid-soluble non-electrolytes, in small amounts also heavy metals, arsenic, etc. Some Poisons (including lipid-soluble non-electrolytes, but also e.g. some heavy metals, including lead) can be excreted through the placenta and act on the fetus. In cases where the transformations and excretion of Poisons occur slowly, with repeated exposure Poisons can accumulate in the body (see Cumulation), and doses that are non-toxic with a single exposure can after some time lead to poisoning (cumulative Poisons). Such material cumulation is distinguished from functional cumulation, when there is no accumulation of Poisons in the body, but a gradual summation of changes caused in cells by repeated exposure to small doses (see Medicines, Combat toxic agents). In many cases it is possible to establish a regular connection between the strength and character of the action and the chemical structure of various Poisons, especially organic ones (see Medicines, Narcotic substances). Among inorganic Poisons, toxicity is often associated with valence (or oxidation state): trivalent arsenic compounds act more strongly than pentavalent ones, and hexavalent chromium compounds (chromates and bichromates) more strongly than two- and three-valent ones (chromic and chromous salts). The toxicity of Poison-electrolytes mostly depends on the degree and character of their electrolytic dissociation: among cyanides, all those that release the CN' ion are highly toxic; some complex cyanide salts (ferrocyanide and ferricyanide) under normal conditions do not form this ion and therefore are little toxic. Along with chemical structure, the action of Poisons is largely determined by their physicochemical properties: it is precisely from these properties (especially solubility) that the concentration of Poisons in the body and their distribution among organs and cells strongly depend. The influence of solubility is very sharply manifested when comparing the action of different gases and vapors, because their solubility in water and blood is extremely different: thus, at body temperature Ostwald's solubility coefficient (ratio of concentration in liquid to concentration in air at saturation) in blood for ethyl alcohol vapors (1,370-1,580) is approximately 100 times greater than for ether vapors (about 15), and 100-125,000 times greater than for nitrogen (0.0125). Therefore, completely different ratios of the strength of action of different Poisons are obtained depending on whether their effective concentrations in air or in aqueous solutions (or blood) are compared. Thus, methane is practically a physiologically indifferent gas; its narcotic action is detected only when it is applied under a pressure of 3-4 atm.; but if narcotic concentrations in blood of methane and other narcotics are compared, it turns out that methane acts several times stronger than alcohol. The influence of solubility on the toxicity of non-volatile Poisons can be seen on the example of lead compounds (the less soluble they are, the less toxic they are), barium (insoluble in water and gastric juice barium sulfate is used in radiodiagnosis; a small admixture of barium carbonate, which dissolves in gastric juice and forms water-soluble barium chloride, causes poisoning), mercury (water-soluble mercuric chloride is much more toxic than calomel), etc. On the other hand, in many cases the action of Poisons themselves is explained by changes in the state of cell colloids or physicochemical changes in tissue fluid. Toxic doses or concentrations of different Poisons are extremely different, in a number of cases very small. Phosphorus can increase gas exchange in rats in doses of 0.01-0.001 mg. Acetylcholine hydrochloride can cause a fall in blood pressure in a cat even in a dose of 0.000002 g per 1 kg weight. In experiments on isolated organs, the action of Poisons in dilutions of 10^-8 (for example of adrenaline on blood vessels of the isolated rabbit ear or on oxygen consumption by tissues) and even larger: 10^-14-10^-18 has been established. But the number of molecules in a gram-molecule of a substance is enormous (6.4×10^23) and therefore even in the latter dilutions in 1 cm^3 of liquid there are still approximately from 50,000 to 10 million molecules. Actions of Poisons in much larger dilutions have been described: 10^-30, even 10^-60 and 10^-100. When evaluating such reports, it should be borne in mind that for example at a dilution of 10^-30 one molecule of Poison would correspond to a volume of liquid that could form a sphere with the radius of Venus's orbit. The correctness of such reports would require a revision of the basic laws of physics and chemistry (Clark). However, this is not necessary, since the action of such extreme dilutions has never been confirmed in control experiments by other authors, and the positive result was obviously explained by experimental errors, especially the difficulty of removing traces of adsorbed poisons from glassware (see also Homeopathy, Oligodynamic action). Between the concentration or dose of poisons and the effect (in cases where the latter can be measured quantitatively) in some cases there is a linear relationship, in others the relationships are much more complex (see Medicines, Doses).

The action of poisons sometimes does not manifest immediately, but after a certain latent period (after a day in poisoning by the death cap, after several hours upon exposure to hydrogen arsenide), which can be explained by the prolonged resorption of the poison or, more often, by the fact that the toxic action belongs to the slowly formed products of the transformation of the poison in the body, etc. The action of poisons can also depend to a large extent on a number of physical factors. An increase in temperature usually accelerates the action of the poison, and the ratio of the speed of action at t°+10° to the speed of action at the given temperature is called the temperature coefficient (Q/10). The value of (Q/10) in interaction with a cell is rarely constant at different temperatures: thus, when determining the rate of stopping an isolated frog heart by strophanthus, Q/10 equaled 3.8 within the temperature range of 7°-17° and 2.1 within the range of 17°-29°. In individual cases, no temperature dependence is found (Q/10 = 1), for example, when determining the rate at which parachlorophenol or formaldehyde kill infusoria. In warm-blooded animals, a change in body temperature, for example, during significant cooling, strongly influences the action of poisons: thus, the convulsive dose of insulin for a mouse decreases 2.6 times when the body temperature drops from 38° to 29°. Some poisons sensitize animals and humans to the action of light (for example, eosin, fluorescein, higher products of dry distillation of coal, mainly pitch) etc. The action of poisons varies depending not only on external but also on internal factors. -The species of animal is of great importance. Some species are very insensitive to certain poisons (for example, the rabbit to atropine). In many cases, especially when poisons act primarily on the nervous system, the sensitivity to the poison is greater the higher the stage of evolutionary development of the given species. Thus, the lethal dose of morphine for a rabbit is approximately 0.3-0.4, and for a human 0.006 g per 1 kg of weight. But it often happens that closely related species react to poisons quite differently: for example, benzene easily causes leukopenia and aplasia of the bone marrow in rabbits and humans, whereas in dogs and guinea pigs leukocytosis and irritation of hematopoietic organs are observed. Plants are distinguished by exceptional sensitivity to some poisons, for example, sulfur dioxide, ethylene. Some heavy metals kill protozoa, algae, etc. in concentrations incomparably lower than those normally found in the human body (see Oligodynamic action). Sensitivity to poisons can also depend on the race of the animal (for example, different races of rabbits are not equally resistant to atropine), the time of year (the difference between winter and summer frogs is well known). Sexual differences in sensitivity have been studied insufficiently.-Sensitivity to poisons can change significantly with age: for example, lethal doses of strychnine are significantly higher for young animals than for adults (for a 10-day-old rabbit 10 times higher than for an adult); conversely, convulsions are caused in young animals by smaller doses.-Individual variations in sensitivity to poisons are sometimes relatively small, sometimes they reach enormous proportions. In humans, particularly large variations in sensitivity are often observed when poisons act on the skin. When two poisons act simultaneously, the action of one component of the mixture can either be enhanced (synergism) or weakened (see Antagonism) by the second component. In this case, the effect can equal the sum or difference of the component effects (summation or subtractive antagonism) or can be significantly greater than this sum or less than the difference (potentiation and depotentiation). More complex relationships are also possible: depending on the doses of the components, synergism or antagonism can be observed, etc. The presence of one poison can lead to an inversion of the action of another, for example, the vasoconstrictive effect of adrenaline in the presence of many substances, depending on the concentrations of H, K, Ca ions, can be replaced by a vasodilatory effect.

With repeated exposure of the organism to a given poison, sensitivity to its action can decrease, habituation to the poison occurs. Habituation is expressed in the fact that to obtain a certain effect it is necessary to use increasingly larger doses of the poison, or in the fact that at the same dose or concentration of the poison the toxic effect manifests itself later and weaker; for example, increasingly larger doses of morphine are needed to reveal its euphoric effect. Habituation can also be expressed in the fact that with chronic poisoning by a given poison, first a gradual deterioration of the general condition of the body is observed, and then, despite the continued exposure to the same doses of the poison, a significant improvement is observed. Habituation to poisons is observed in organisms standing at the most diverse stages of evolutionary development, including in Protozoa, and it develops with varying ease in representatives of different classes. Habituation in Metazoa, particularly in humans, is little known in relation to inorganic poisons with resorptive action. The most well-known example is habituation to arsenic. It is apparently explained by the weakening of the resorption of arsenic in the intestine, since 'habituated' animals die from ordinary lethal doses of this substance when it is administered subcutaneously. In general, it is not possible to increase the resistance of an animal to As (see Arsenic) by subcutaneous injections. 'Local' habituation of mucous membranes to irritating gases (for example, chlorine, hydrogen chloride, sulfur dioxide, etc.) is also often described, and in this case the latter by no means means simultaneous habituation to the resorptive action of the same gases, if such exists.

712: e.g. experiments with the introduction of carbonic acid or carbamic acid ammonium per os show that animals do not become accustomed to the resorptive action of ammonia. More is known about addiction to organic poisons. The most well-known example is addiction to morphine, which can be achieved by any method of introducing the poison into the organism, as well as in in vitro experiments (tissue cultures). The mechanism of addiction is often explained by the faster breakdown of morphine in the bodies of 'accustomed' animals or people; recent research has shown that this mechanism is much more complex (see Morphine). No addiction is observed to some chemically similar derivatives of morphine, e.g. codeine, dionine. Addiction to some narcotically acting poisons (alcohol, ether, gasoline) is well known, and here also phenomena of group and cross-addiction are known; it is known that alcoholics are difficult to anesthetize; addiction to one grade of gasoline also means increased tolerance to other grades, despite significant differences in chemical composition. Addiction to some drugs (alcohol) is partly explained by their increased breakdown in the body, while in relation to others (chemically indifferent hydrocarbons contained in gasoline) it is due to direct addiction to the action of the poison on cells, especially the nervous system. Addiction to poisons of different organs and systems can proceed quite unevenly: in a tolerant dog, the respiratory center may not react to a 1,800-fold initial effective dose of morphine, while at the same time no addiction to this alkaloid is observed from the vagus center. Sometimes upon removal of the poison to which addiction has occurred (e.g. upon cessation of morphine intake by a morphinist), characteristic disorders may be observed, the so-called withdrawal symptoms (Abstinenzerscheinungen) (see Morphine, morphinism).-Often with repeated exposure of poisons to the body, not an increase but a decrease in tolerance is observed: for example, with repeated poisonings of animals with hydrogen sulfide, convulsions are observed earlier each time. Some poisons after repeated exposure cause in the body a state of increased sensitivity to them, manifested by special diseases not observed in other 'non-sensitized' individuals: eczema from aromatic amines, which can form quinoid compounds in the body, vasomotor rhinitis and bronchial asthma from paraphenylenediamine, etc. (see Allergy, Sensitization). I. Lazarev. The isolation of poisons is reduced to four methods: 1) isolation of substances that distill with steam; 2) isolation by destruction of organic substances and reduction of the study to methods of inorganic analysis; 3) isolation by extraction of substances with acidified alcohol; 4) extraction with water. Distillation with steam can isolate hydrocyanic acid, aniline, nitrobenzene, benzene hydrocarbons, phenols, formaldehyde, methyl alcohol, ethyl alcohol, fusel oils, carbon disulfide, chloroform, carbon tetrachloride, chloral hydrate, and phosphorus. The ground object is placed in a flask set on a water bath, and by slowly passing steam through it, distillation is carried out, collecting separate portions. The first portion of distillate (2-5 cm³) is collected in a diluted solution of caustic alkali and tested for hydrocyanic acid. The remaining parts of the distillate are tested for other poisons. Destruction of organic substances is carried out: 1) with the help of hydrochloric acid and potassium chlorate (destruction by chlorine at the moment of evolution) and 2) with sulfuric and nitric acids, the latter being taken in the form of ammonium nitrate (method of A. Stepanov). Insufficient destruction of carbohydrates occurs when using the first method. The research object is placed in a flask, mixed with approximately 12% hydrochloric acid, and potassium chlorate is added in small portions while heating on a water bath. Heating and addition of potassium chlorate usually continues from 15 to 60 hours and ends when the color of the liquid does not change upon heating without adding a new portion of potassium chlorate. Incomplete destruction, premature termination of work can lead to the concealment of mercury in further research. The liquid is then diluted with water to a content of 2% hydrochloric acid (approximately) and heated on a slightly heated water bath until chlorine is removed, filtered. The heated liquid is then precipitated with hydrogen sulfide, and for special research on small amounts of mercury, copper spirals are placed in the liquid, on which mercury precipitates. The second method can only be applied to small volumes and is especially necessary for the destruction of hydrocarbons: flour, cereals, etc. The ground object is placed in one or more Kjeldahl flasks and poured with five times the amount of concentrated sulfuric acid. The flasks are heated on a flame with a grid, adding ammonium nitrate in small portions so that nitrogen oxides do not escape from the flask opening. Heating is continued until the liquid becomes colorless and transparent. It is then mixed with ten times the amount of water, whereby lead, barium sulfates, and sometimes (when destroying bony fish) calcium may precipitate. The filtrate is tested for substances that may be poisons. Extraction with acidified alcohol is used in the analysis for alkaloids. The purpose of the alcohol is to precipitate proteins, and acidified alcohol dissolves the salts of alkaloids. For acidification, tartaric or oxalic acid is used. The alcoholic extract is evaporated in a vacuum or on a slightly heated (up to 40°) water bath to the consistency of syrup. The latter is treated with alcohol (96° or absolute), adding in small portions until proteins coagulate. The liquid is then filtered and evaporated again as described above. The operation is repeated until the alcohol no longer precipitates anything. The syrupy liquid is then diluted with a small amount of water and the resulting solution (it should have an acidic reaction) is repeatedly extracted with small portions of chloroform. The extraction aims to purify the liquid for subsequent extraction of alkaloids, but with appropriate indications it serves to isolate substances extracted from an acidic solution, such as acids: picric, salicylic, cantharidin, polyhydric phenols such as hydroquinone, then phenacetin, antifebrin, and other substances. Traces of alkaloids may pass into the chloroform from the acidic solution, especially strychnine, which may sometimes not be detected from an alkaline solution when only a trace is present in the object under investigation. The acidic aqueous liquid is then basified with ammonia and again extracted with chloroform. The chloroform extracts, combined together, washed with small portions of water, filtered through a dry filter, are evaporated at room temperature. The residue is subjected to purification. For this, it is dissolved in a small amount of water with the help of as small an amount as possible of very dilute hydrochloric acid (e.g. 1%), the solution is filtered, and again extracted with chloroform. The aqueous liquid is basified with ammonia and again extracted with chloroform. The operation is repeated. The chloroform extract from the alkaline solution is then evaporated and the residue is tested for alkaloids. Extraction with water is only done when the autopsy protocol, circumstances of the case, or preliminary tests give indications for this. The object is mixed with distilled water to form a liquid mush, the liquid is filtered and subjected to research. Sometimes the obtained mush is subjected to dialysis (when testing for salts). With the filtrate of the aqueous extract, research is carried out on mineral acids (sulfuric, hydrochloric, nitric), caustic alkalis, on salts of chloric acid (mainly potassium chlorate), nitrites, fluorides, oxalic acid and its salts.