STERILISATION. 27 



technical work. Like most of the other mercuric salts, mer- 

 curic chloride belongs to that class of bodies which produce 

 insoluble compounds with albuminoids, and thus do not react 

 completely with bacteria. Attempts have been made to 

 overcome this difficulty in such cases by the addition of a 

 small percentage of sodium chloride. Hydrofluoric acid and 

 its salts also belong to the most powerful antiseptics, especially 

 as regards bacteria. Ammonium fluoride is generally used, 

 and has a wide application. Chlorine is used in the fermenta- 

 tion industry in the form of chloride of lime, but it is only 

 applicable within certain narrow limits, owing to its strong 

 and pungent odour. Another compound, sodium hypochlorite 

 (antiformin), which has a weaker smell of chlorine, is more 

 widely used. Chlorine is also used to disinfect water. For 

 this purpose small quantities of chloride of lime are used, and 

 after a short time the chlorine is fixed by the addition of 

 calcium bisulphite. Sulphurous acid is used sometimes in 

 the form of gas or of an aqueous solution, and sometimes as 

 calcium bisulphite or sodium sulphite. It is used, not only as 

 an antiseptic, but also as a means of restricting fermentative 

 activity. This, as well as several of the above, usually appears 

 to attack bacteria more strongly than yeasts in high dilutions. 

 Soda is of value as a means of cleansing, as well as disinfecting, 

 and this applies also to lime. Lastly, two gases must be 

 mentioned which are now coming into use, ozone and hydrogen 

 peroxide, the latter having an even greater disinfecting power 

 than ozone. 



Amongst organic antiseptics, formaldehyde has found very 

 extended application during the last few years, on account of 

 its great antiseptic power. Thus, the spores of many resistant 

 bacteria are killed by the application of a 1 per cent, solution 

 for an hour. On the other hand, this reagent, when used in 

 the form of vapour, has little action on man and the higher 

 animals. Its vapours appear principally to attack the surface 

 of articles, as its power of penetration is not great. 



A series of antiseptics which have proved of special im- 

 portance in laboratory studies of fermentation includes ether, 

 chloroform, and more especially acetone, toluol, and thymol, 

 because they possess the valuable property that, while they 



