DISINFECTION AND DISINFECTANTS 257 



efficiency varies not only with their active ingredients, but 

 also with the character of the emulsion which they form, 

 from about the same as that of phenol to about three 

 times as much. Commercially they are known as soluble 

 carbolic acid, soluble creosote, etc. Creolin is a type of 

 numerous preparations of the same character. They are 

 all poisonous and sensitive to proteins. If naphthalene 

 is present in excess, it is deposited on standing in cold 

 weather. Lysol contains 50 per cent, of the cresols in 

 fat or linseed oil saponified with addition of alcohol. 

 It gives a clear solution with water, having slightly less 

 efficiency on naked bacteria than cresol, much superior 

 solvency for grease, and equal sensitiveness to proteins. 

 Many preparations of the same type are now sold, and are 

 convenient for such laboratory purposes as disinfecting 

 slides and glass apparatus after use. 



Liquor cresolis saponatus (British Pharmacopoeia, 

 1914) consists of cresylic acid 50 per cent, dissolved 

 in castor oil and saponified with potassium hydrate. 



A new era in chemical disinfection began when Ainslie 

 Walker first prepared cyllin, which contains oxidised 

 hydrocarbons possessing a diphenyl nucleus, emulsified 

 with a neutral hydrocarbon oil. A large number of 

 emulsified disinfectants can now be obtained kerol, 

 M.O.H. fluid, bactox, and cofectant being the most reliable. 



It should bo noticed that the use of water containing 

 very high total solids (e.g., sea- water) reduces the efficiency 

 of these preparations, and special articles, in which glue 

 is used as a base, are made for such waters; but all such 

 preparations require to be agitated before dilution, owing 

 to the fact that they separate out on standing into layers 

 of very different efficiency. 



Salicylic acid was formerly used as a preservative for 

 milk and milk products. It is still used for preserving 

 jams and lime-juice. It has recently been used as a 

 dressing for wounds. Thymol is a strong disinfectant 

 that enters into the composition of many mouth-washes 

 and tooth-pastes. 



Disinfectant Powders. 



If a suitable powder be sprinkled on manure-heaps, 

 dustbins, or in pail-closets or privies, not only are foul 

 odours absorbed, but flies are kept away, and prevented 



