156 BACTERIOLOGY. 
A BRIEF DESCRIPTION OF SOME OF THE MORE 
COMMONLY USED DISINFECTANTS. 
Bichloride of Mercury. This substance, when present 
in 1 part in 1,000,000 in nutrient gelatin or bouillon, 
prevents the development of parasitic bacteria. In 
water 1 part in 500,000 will kill many varieties in a 
few minutes, but in bouillon twenty-four hours may 
be needed. With organic substances its power is less- 
ened, so that 1 part to 1000 may be required. Spores 
are killed in 1 to 1000 watery solution within one hour. 
Corrosive sublimate, as seen in the figures given above, 
is less effective as a germicide in alkaline fluids con- 
taining much albuminous substance than in watery 
solution. In such fluids, beside loss in other ways, 
precipitates of albuminate of mercury are formed 
which are at first insoluble, so that a part of the mer- 
curic salt does not really exert any action. In alkaline 
solutions, such as blood, blood-serum, pus, tissue-fluids, 
etc., the soluble compounds of mercury are converted 
into oxides or hydroxides. The soluble compounds 
can, of course, remain in solution only when there are 
present sufficient quantities of certain bodies which 
render solution possible. Bodies of this sort are espe- 
cially the alkaline chlorides and iodides, and, above all, 
sodium chloride and ammonium chloride. A very 
simple way of preventing precipitation of the mer- 
cury, then, is to add a suitable quantity of common 
salt to the corrosive sublimate. ‘Those compounds of 
mercury which, like the cyanides, are not precipitated 
with alkalies, because they at once form double salts, 
require no addition of salt. 
For ordinary use, where corrosive sublimate is em- 
