Wood Antiseptics

WOOD ANTISEPTICS, substances or mixtures possessing the ability to inhibit the development of biological pests of wood. Being one of the most durable organic natural materials, wood in certain cases is rapidly destroyed by the life activity of biological pests, primarily saprophytic fungi, then worms, beetles, some mollusks, etc. The degree of harm caused by the "rotting" (actually, decay) of wood can be characterized by the fact that in Russia, despite its poorly developed railway network and abundance of forests, before the war the replacement of railway ties cost annually 12-15 million rubles, and approximately the same amount was estimated as the losses caused by harmful fungi to buildings. The house fungus (Merulius lacrimans and others) can destroy a newly painted and plastered building within 2-3 years. It mainly affects those parts of the building where moisture accumulates (lower logs, cellars, floors, toilets, walls of laundries, etc.); from here the infection spreads throughout the building, and penetrates into the upper floors of stone buildings along wooden parts. The first information about the most dangerous of the pests (Merulius) dates back to the 17th century. The feverish growth of urban construction in the 18th century, due to non-compliance with the basic requirements of building hygiene, led to the extremely rapid spread of the house fungus and to the development of the issue of preventing this infection. From 1700 to 1876, means for wood conservation were proposed by more than 235 inventors. The various proposed methods can be divided into the following groups: a) steaming of wood with steam, b) vulcanization, c) charring, d) fumigation, e) coating and painting with various oils and compositions, f) immersion in various oils and mineral and organic solutions, g) impregnation under natural pressure with various organic and inorganic substances, h) treatment with vapors of resinous antiseptics and removal of sap from wood, i) electrosmotic impregnation, j) impregnation using drilled small holes, k) impregnation using vacuum and pressure. With the exception of the not entirely clear group of wood steaming methods, all the others are based on the ability of antiseptics to inhibit the development of wood pests; hence groups b), c), and d) are no exception, as they are associated with the formation of antiseptics from the wood itself when heated. Of the proposed antiseptics, most did not enter practice either because of their high cost, or because of their inability to be firmly retained in the wood, or because of the difficulty of introducing them into the wood, or because of harmfulness to workers involved in impregnation (and generally having contact with impregnated wood), or because of their effect on impregnation vats and metal in contact with impregnated wood, or because of weakening of the mechanical properties of the wood, or finally because of the weakness of the antiseptic strength of the substance, usually expressed as a fraction ^s/_# (where p is the amount of antiseptic in grams per 100 cubic cm of nutrient liquid necessary to inhibit the development of the fungus Penicillium, and g is the amount of the same antiseptic in kilograms per 1 cubic cm of wood introduced during the conservation process). The most effective antiseptics, despite the enormous variety of various patented means, come down to a few typical representatives or their combinations. 1. Various phenols either in pure form or in mixtures with naphthalene, anthracene, oils and resins; these mixtures are obtained by dry distillation of wood, peat, coal, oil shales, etc. Being tested and reliable antiseptics, phenolic substances also have negative sides: some costliness, unpleasant odor and harmfulness of work with them, difficulty of introduction into wood. 2. Chrome salts, for example, sodium bichromate, usually used in combination with other antiseptics, for example, tar pitch ("chromtar"), dinitrophenol-aniline ("triolite", "minolite") etc. 3. Sodium fluoride, rarely used alone, as it is easily washed out by water, but in combination with dinitrophenol compounds gives good results; such are, for example, patented means: basilite, minolite, tanalite, triolite, fluoxite, sillite. 4. Dinitrated phenols and their derivatives, for example, dinitrophenol, sodium dinitroorthocresolate, etc., according to experiments proved to be perhaps the best antiseptics. The preserving function in these complex antiseptics (basilite, malenite, minolite, tanalite, triolite, fluoxite, sillite of marks S_m and S_k) is first carried by the rapidly spreading but also rapidly washed out sodium fluoride, and then by the slowly spreading but firmly inhibiting phenol derivative. Antiseptics of this kind color wood yellow; to one degree or another they somewhat affect iron. Wood impregnated with them does not show signs of decay even in mine conditions after 7 years. 5. Thio-compounds, for example, creosote "S", obtained in the treatment of crude oil with sulfur, similar products extracted from sapropelic resin, etc., were found to possess significant bactericidal power and apparently have data for practical use. 6. Naphthenic acids and their salts, especially copper salt, also showed good antiseptic qualities, however, they have not yet been sufficiently studied under practical conditions. 7. Zinc chloride, long known and widely used as an antiseptic, has its advantageous sides, but its bactericidal power and retention by wood are small. 8. Copper sulfate is also one of the old antiseptics; in its qualities it is close to the previous one. 9. Sublimate is an antiseptic long known and stronger than copper sulfate and zinc chloride, however, it is significantly inferior to nitrated phenols.