X. 

 ACTION OF SALTS. 



WHILE some of the metallic salts, and especially those of mer- 

 cury, silver, and gold, have remarkable germicidal power, others, 

 even in concentrated solutions, do not destroy the vitality of bacteria 

 exposed to their action. For convenience of reference we shall con- 

 sider the agents in this group in alphabetical order, but first we give 

 Miquel's tables of antiseptic value. This author recognizes the im- 

 portance of experiments to determine the restraining power of chem- 

 ical agents for various species of pathogenic bacteria, but says : ' ' As 

 to me, faithful to a plan I adopted at the outset, I will treat the sub- 

 ject in a more general manner by making known simply the mini- 

 mum weight of the substances capable of preventing the evolution of 

 any bacteria or germs. The method adopted is very simple. To a 

 liquid always comparable to itself it is sufficient at first to add a 

 known weight of the antiseptic and some atmospheric germs or adult 

 bacteria, and to vary the quantity of the antiseptic until the amount 

 is ascertained which will preserve indefinitely the liquid from putre- 

 faction. In order to obtain germs of all kinds in a dry state it suf- 

 fices to take them, where they are most abundant, in the dust col- 

 lected in the interior of houses or of hospitals; and to procure a 

 variety of adult bacteria we may take the water of sewers. " 



SUBSTANCES EMINENTLY ANTISEPTIC. 



Efficient in the 

 proportion of 



Mercuric iodide, . . . . . . 1 : 40000 



Silver iodide, ...... 1:33000 



Hydrogen peroxide, . . . . . 1 : 20000 



Mercuric chloride, . . . . . 1 : 14300 



Silver nitrate, . . 1 : 12500 



SUBSTANCES VERY STRONGLY ANTISEPTIC. 



Osmic acid, . . . . . . 1 : 6666 



Chromic acid, . . . . . . . 1 : 5000 



Chlorine, ...... 1:4000 



Iodine, ....... 1:4000 



Chloride of gold, . ..... 1:4000 



Bichloride of platinum, . . . . 1 : 3333 



Hydrocyanic acid, . . . . . 1 : 2500 



