BACTERIOLOGY IN A NUTSHELL. 
Formalin Solution. A four per cent, solu¬ 
tion of formalin is considered to be as effective 
as bichloride of mercury solution i-iooo, or as 
carbolic acid solution 1-20 ( 5 %). Formalin 
contains formaldehyde forty per cent, and wood- 
alcohol ten per cent. Unlike bichloride of mer¬ 
cury it does not deposit albuminous substances in 
solution, but it destroys iron, steel or other metal 
quite as effectually. The four per cent, solution 
is prepared by adding forty-one drams to each 
gallon of water. (For number of grains to use 
for each pint of solution see table at close of 
Chapter VII.) 
Boracic Acid is a mild, non-irritating antisep¬ 
tic used freely in irrigation and in surgery of 
the eye and ear. Many surgeons use a saturated 
solution; others prefer a solution of one dram 
to each pint of water. It is dissolved by pour¬ 
ing hot water over the acid powder. It does not 
dissolve readily in cold water. In fact it would 
better be boiled. In making the saturated solu¬ 
tion, it has been found that only about eighteen 
grains of the powder to each ounce of water is 
soluble in water alone. 
The American Standard. A solution known 
as the “American Standard” is made by dissolv¬ 
ing six ounces of chloride of lime in one gallon 
of water. It is said to be valuable in the disin¬ 
fection of excreta. Chloride of lime in order to 
be reliable must be purchased of a reliable man¬ 
ufacturer. 
Thiersch's Solution. In the preparation of 
this solution, which is often used as an antiseptic 
for purposes of irrigation, add one and a half 
ounces of boracic acid and two drams of salicylic 
88 
