4A a MIDLAND NATURALIST 
The Preparation of Absolute Alcohol for Histological 
and Chemical Purposes.* 
ALBERT T. MERTES. 
A cheap and convenient method of preparing absolute alcohol 
for histological purposes on a small scale in a school or college is 
much needed. The ordinary methods given in text-books of 
organic chemistry require a considerable amount of apparatus and 
many different appliances which an ordinary biological laboratory 
might not conveniently have, and it is because of this fact that the 
_ following method has been devised. 
rdinary commercial alcohol about 9o to 95 per cent. strong is 
placed in a bottle or flask and small quantities of calcium carbide 
added at different intervals of time dependant on the rapidity with 
which the carbide is attacked, —about once in six hours is sufficient; 
if the mixture be placed in a warm place, however, the action is 
much more rapid. 125 grams may be added at the beginning of 
the operation, and 25 grams at a time every 5 or 6 hours thereafter 
until the reaction is finished. "This point may be recognized both 
by the cessation of the appearance of bubbles of acetylene, or from 
the fact that the freshly added carbide remains several hours un- 
acted upon. 
The carbide acts upon the water in the alcohol, forming slaked 
lime and acetylene. (Reaction) CaC,+2H,0=Ca (OH),4-C;H 
When it is dehydrated the action ceases. During the process the 
mixture should not be shaken. or agitated, because the slag or 
residue of slaked lime becomes suspended in the liquid and settles on 
the added portions of carbide thus preventing further action. If 
the carbide is added at different intervals it spreads out upon the 
sities idue forming a layer that will be acted upon. 
Wika the last layer of carbide remains unchanged after being 
in contact with the alcohol for some hours, the action is considered 
complete. If much matter remains suspended in the liquid, the 
mixture is allowed to stand a little longer tiM the supernatant liquid 
is clear and well settled. The alcohol is now carefully decanted 
or siphoned into a dry bottle and kept therein until used. 
* Extract from thesis for the Bachelor's degree in Science. I wish to thank 
my professor, Dr. J. A. Nieuwland, who suggested the subject of this thesis. 
