144 BACTERIA IN AIR, SOIL, AND WATER. 



effects described are not due to a very complicated action of free 

 hydrochloric acid, hydriodic acid, and of oxyacids of chlorine 

 and iodine produced by its decomposition. It is stated, how- 

 ever, that the action is very potent : a i per cent solution is 

 said instantly to kill even anthrax spores, but if the spores be in 

 bouillon, death occurs after from ten to twelve minutes. In 

 serum the necessary exposure is from thirty to forty minutes. 

 A solution of i-iooo will kill the typhoid, cholera, and diphtheria 

 organisms in five minutes. • 



Nascent Oxygen. — This is chiefly available in two ways — 

 firstly, when in the breaking up of ozone the free third atom of 

 the ozone molecule is seeking to unite with another similar atom ; 

 secondly, when peroxide of hydrogen is broken up into water 

 and an oxygen atom is thereby liberated. In commerce the 

 activity of " Sanitas " compounds is due to the formation of 

 ozone by the slow oxidation of the resin, camphor, and thymol 

 they contain. 



Perchloride of Mercury. — Of all the salts of the heavy met- 

 als this has been most widely employed, and must be regarded 

 as one of the most powerful and useful of known antiseptics. 

 In testing this action on anthrax spores there is no doubt that in 

 the earlier results its potency was overrated from a neglect of 

 the fact already alluded to, that in the spore-case an albuminate 

 of mercury was formed which prevented the contained proto- 

 plasm from developing, while not depriving it of life. It has 

 been found, however, that this salt in a strength of i-ioo will 

 kill the spores in twenty minutes, although an hour's exposure 

 to i-iooo has no effect. The best results are obtained by the 

 addition to the corrosive sublimate solution of .5 per cent of sul- 

 phuric acid or hydrochloric acid ; the spores will then be killed 

 by a seventy-minute exposure to a 1-200 solution. When, how- 

 ever, organisms in the vegetative condition are being dealt with, 

 much weaker solutions are sufficient; thus anthrax bacilli in 

 blood will be killed in a few minutes by 1-2000, in bouillon by 

 1-40,000, and in water by 1-500,000. Plague bacilli are killed by 

 one to two minutes' exposure to 1-3000. Generally speaking, it 

 may be said that a 1-2000 solution must be used for the practically 

 instantaneous killing of vegetative organisms. 



Perchloride of mercury is one of the substances which have 

 been used for disinfecting rooms by distributing it from a spray 



