210 VETERINARY HYGIENE 



known reliability. In fact it is safer to regard whitewash rather as 

 a medium for carrying and applying a disinfectant than as being 

 itself a disinfectant. Carbolic acid or any of the phenol prepara- 

 tions are most suitable for this purpose. Carbolic acid should be 

 added so that the wash contains 5 per cent. ; the emulsified coal-tar 

 products, being more potent, should be added so the mixture 

 contains from 2 to 3 per cent. In every case the container in 

 which the whitewash is mixed should have its capacity estimated so 

 that addition of the active disinfecting agent is not a matter of 

 guess work. 



Whitewash should never be applied to dirty greasy walls for the 

 purpose of hiding dirt. Previous to application a thorough cleans- 

 ing should be carried out. The addition of size, salt, fat or alum to 

 the mixture prevents the dried lime from rubbing off. 



Whitewash may be applied with a brush or by means of a spray- 

 ing machine; in either case it is difficult to get the mixture to 

 penetrate sufficiently into the cracks and crevices. When spraying 

 a disinfectant on to walls, stall partitions, &c., it is important to 

 apply the spray with force; this is not possible with whitewash 

 owing to the mechanical nature of the suspension. 



Lime, as quicklime or milk of lime, is particularly suitable for 

 use about dairies and cowsheds; it possesses itself deodorant pro- 

 perties, and does not impart an odour to milk which very readily 

 becomes tainted by chloride of lime and some other disinfectants 

 of value. 



The following method of making limewash is recommended by 

 the Department of Agriculture of New South Wales : 



Place enough tallow required for the purpose in a large bucket, 

 then lay the same quantity of dry lime on top of the tallow, then 

 enough water to slake the lime. When the heat from the lime has 

 melted the tallow and all is dissolved, stir thoroughly until well 

 mixed; then apply, -while still warm, with a brush. The surface 

 must be dry and clean before the wash is applied. 



FORMALDEHYDE, Formalin (HCHO). Formalin is a 40 per 

 cent, solution of formaldehyde gas. It is used as a liquid, a 

 vapour or a gas. 



Pure formalin is a colourless liquid yielding a colourless vapour. 

 Some of the commercial formalin has a yellowish tinge. The 

 vapour given off is irritating to the eyes, nose, and throat, and, if 

 sufficient be inhaled, to the bronchi. Compared with other gaseous 

 or vapour disinfectants it is much less harmful to the higher 

 animals, while at the same time it possesses a powerful disinfectant 

 property. Its action is slow and uncertain at a low temperature, 



