XVII. MISCELLANEOUS PKODUCTS USED IN AGRICULTUEE 369 



Many other antiseptic and disinfectant substances have been ob- 

 tained from coal-tar. For an account of these substances, a treatise on 

 organic chemistry should be consulted. 



"Formalin" the commercial name for a solution of formaldehyde, 

 H 2 CO, in water. The nominal strength is 40 per cent of formaldehyde, 

 and a trace of formic acid is also present. The liquid is stable in 

 closed vessels, but loses the gas on free exposure to air. 



Formaldehyde is one of the most powerful antiseptics and disin- 

 fectants. Solutions of 1 in 10,000 or 20,000 will prevent the growth 

 of many micro-organisms and 1 per cent solutions produce absolute 

 sterility. 



Formaldehyde is an admirable fungicide and, in sufficient quantities, 

 acts as a powerful plant poison. 



In 1897 Windisch x investigated the effect of various strengths of 

 formaldehyde solutions upon the germination of cereals. In each 

 case, 200 seeds were allowed to germinate between pieces of thick 

 filter paper moistened with water and with 0*02, - 04, 0*08, 0*12, 

 0'20 and 0'40 per cent formaldehyde solutions respectively. 



Wheat was almost wholly destroyed by the 0'12 per cent solution, 

 whilst oats were only delayed in their germination by this solution ; 

 with 20 per cent solutions, barley, wheat and rye were destroyed, and 

 with 0'40 per cent solutions, oats also succumbed. In 1901, he 2 ex- 

 tended the experiments to other seeds ; the 0'2 per cent solution killed 

 flax and rape and greatly injured lupines, peas and clover, retarded the 

 germination of horse-beans, but did not injure maize. Even a 0*4 per 

 cent solution, which killed all other seeds, did not destroy maize. 



By shorter treatment of seeds with formaldehyde, it has been at- 

 tempted to destroy the smut spores in grain without injuring the seed, 

 Kinzel 3 found that a O'l per cent solution of formaldehyde applied for 

 one hour to rye, wheat, oats, barley, clover and lupines had no injurious 

 effect upon the seed, but destroyed, almost completely, the spores of 

 fungi. 



" Formalin " has been used as a preservative for foodstuffs milk, 

 butter, etc. ; but since it combines with proteids and also has an in- 

 hibitive effect upon enzymes, its use for this purpose is not to be recom- 

 mended. 



Fungicides. These are, in nearly all cases, plant poisons, but are 

 used under such conditions or in such dilute solution that they do not 

 injure the higher plants. Some of the more important fungicides are 



Copper salts, vide p. 362. 



Ferrous sulphate, vide p. 372. 



Mercuric chloride. This has been recommended and used in 

 America as a remedy for bunt or stinking smut in wheat. The seed is 

 treated with a 0'2 per cent solution, conveniently made by dissolving 

 1 Ib. of corrosive sublimate in 50 gallons of water. 



Formaldehyde, vide above. For prevention of bunt in wheat or 



!Landw. Versuchs-Stat., 1897, 223; Jour. Chem. Soc., 1898, Abstracts, ii. 40. 

 2 Ibid., 1901, 241 ; Jour. Chem. Soc., 1901, Abstracts, ii. 466. 

 3 Ibid., 1898, 461 ; Jour. Chem. Soc., 1898, Abstracts, ii. 302. 



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