THE EFFECTS OF CEKTAIN ANTISEPTICS 171 



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

 contain. 



Perchloride of Mercury.— Of all the salts of the heavy metals this has 

 been most widely employed, and must be regarded as one of the most 

 powerful and useful of known antiseptics. In testing its 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 

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

 found, however, that this salt in a strength, of 1-100 will kill the spores 

 in twenty minutes, although an hour's exposure to 1-1000 has no effect. 

 The best results are obtained by the addition to the corrosive sublimate 

 solution of "5 per cent, of sulphuric acid or hydrochloric acid ; the spores 

 will then be killed by a seventy-minute exposure to a 1-200 solution. 

 When, however, 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 has been used 

 for disinfecting rooms by distribution from a spray producer, of which 

 the Equifex may be taken as a type. With such a machine it is 

 calculated that 1 oz. of perchloride of mercury used in a solution of 

 1-1000 will probably disinfect 3000 square feet of surface. Such a 

 procedure has been extensively used in the disinfection of plague houses, 

 tut the use of a stronger solution (1-500 acidulated) is probably 

 preferable. 



Formalin as a commercial article is a 40 per cent, solution of formalde- 

 hyde in water. This is a substance which of late years has come much 

 into vogue, and it is undoubtedly a valuable antiseptic. A disadvantage, 

 however, to its use is that, when diluted and exposed to air, amongst 

 other changes which it undergoes it may be transformed, under little- 

 understood conditions, into trioxymethylene and paraformaldehyde, 

 these being polymers of formaldehyde. The bactericidal values of these 

 mixtures are indefinite. Formalin may be used either by applying it in 

 its liquid form or as a spray, or the gas which evaporates at ordinary 

 temperatures from the solution may be utilised. To disinfect such an 

 organic mixture as pus containing pyogenic organisms, a 10 per cent, 

 solution acting for half an hour is necessary. In the case of pure cultures, 

 a 5 per cent, solution will kill the cholera organism in three minutes, 

 anthrax bacilli in a quarter of an hour, and the spores in five hours. 

 When such organisms as pyogenic cocci, cholera spirillum, and anthrax 

 bacillus infect clothing, an exposure to the full strength of formalin 

 for two hours is necessary, and in the case of anthrax spores, for twenty- 

 four hours. Silk threads impregnated with the plague bacillus were 

 found to be sterile after two minutes' exposure to formalin. 



The action of formalin vapour has been much studied, as its use con- 

 stitutes a cheap method of treating infected rooms, in which case some 

 spray-producjng machine is employed. It is stated that a mixture of 

 8 c.c. of formalin with 48 c.c. of water is sufficient when vaporised to 

 disinfect one cubic metre, so far as non-sporing organisms are concerned. 

 It is also stated that 1 part formalin in 10,000 of air will kill the cholera 



