On jDisinfectants. 95 



1, On vabious Disinfectants — their Mode of Action and 



TRACTICAL UtILITT. 



a. True Disinfectants. 



Tlie following are some of the best known true disinfectants : — 



Chloride of lime, chlorine gas, sulphurous acid, nitric acid, nitrous 

 acid, quick lime, soda ash, wood and peat charcoal, dry earth, man- 

 ganate and permanganates of potash or soda (Condy's disinfectant), fii-e, 

 heat, and air. 



All true disinfectants, as stated already, destroy more or less rapidly 

 organic matters. On account of the rapidity with which some exert 

 their power, they are highly injurious to animal life, and therefore 

 cannot be used in cowsheds or stables in which animals are kept at 

 the time when disinfection has to be practised. 



Others destroy organic matters only slowly, but in the end most 

 effectually ; and still others dissolve infectious matters readily, but, 

 unlike chlorine or nitric acid, act ujion it very gradually. These 

 differences ' in the actions of disinfectants, and their general applic- 

 ability or their use in special cases, will best appear as we go through 

 the list given above. 



Chloride of Lime. — Slaked lime absorbs large quantities of chlorine 

 gas, and becomes changed into hypochloride of lime and chloride of 

 calcium. Both these combinations, with more or less unchanged 

 quick lime, carbonate of lime, and even all the impurities originally 

 present in the quick lime employed, are present in chloride of lime or 

 bleaching-powder ; a preparation which is made] by passing chlorine 

 gas into slaked lime, so as to saturate it more or less completely. 

 The active principle is hypochloride of lime, which is readily decom- 

 posed by all mineral acids. Even the weak carbonic acid, always 

 present in ordinary air, acts ujion it, forming carbonate of lime and 

 disengaging hypochlorous acid. Chlorine and oxygen, the consti- 

 tuent elements of hypochlorous acid, are held together in this acid 

 but very feebly; in consequence of which it readily splits into free 

 oxygen and chlorine gas. Chloride of lime of commerce thus is a pre- 

 paration which merely on exposure to a moist air gives off oxygen in a 

 nascent condition and chlorine gas, which is distinguished from most 

 other elementary gases by its great affinity for hydrogen. 



Chlorine unites not only with great violence with pure hydrogen, 

 but it also takes hydrogen from its combination with other substances. 

 In most organised substances, carbon, hydrogen, and oxygen are never- 

 failing constituents. The hydrochloric acid is very raj)idly destroyed, 

 or rather it breaks up very rapidly into free oxygen and chlorine ; two 

 gases which, acting ujion meat and nearly all animal and vegetable 

 matters, burn and disorganise them completely. If we take a piece of 

 meat and boil it well in chloride of lime for a sufficient time, it is 

 altogether destroyed, and disaj)j)ears, being resolved into gaseous and 

 comparatively harmless products. This is unquestionably one of the 

 most active and most available artificial disinfectants we can use, 

 either for disinfecting carcases or for brushing over the walls and 

 floors of tainted sheds. For sucli uses, mix 1 lb. of chloride of lime 



