MIDLAND NATURALIST. 45 
Alcohol prepared in this manner is completely dehydrated but 
contains as an impurity acetylene gas, some lime in solution, also 
some traces of organic sulphur compounds. The alcohol though 
clear may be of a strong yellow color due to these compounds 
especially so when denatured alcohol is used. ‘This color, however, 
is not objectionable when the primary end is to obtain an absolute 
alcohol for histological purposes. The acetylene may be almost 
entirely removed by warming the liquid to about 75? C. This may 
be easily accomplished by placing the bottle on a steam radiator 
for two or three hours till the heat drives the gas out of solution. 
The acetylene that remains does not affect thereagents nor mounts. 
The lime disolved is not appreciable, being about 1 part by weight 
in 30,000 of alcohol by volume. ough this alcohol is not strictly 
pure, the presence of lime is not deleterious, but on the contrary is 
beneficial. The alkali appears to fix the dye into the section to be 
stained so that the color of the tissue does not fade. The reason is 
that most of the dyes used in staining have basic properties and the 
color is intensified or made more permanent by an alkali, and the 
dissolved lime answers this purpose, as already noted. * 
] Where it is impracticable to use dehydrated alcohol containing 
lime or acetylene in solution, the alcohol may be further purified by 
subjecting it to distillation, thus getting rid of the dissolved im- 
purities from the action of the commercial carbide which is rather 
impure. On account of the solubility of acetylene in alcohol 
there will be a small amount found in the distillate. This is re- 
moved by adding a little finely-powdered and dried silver and 
mercuric nitrate or mercuric oxide. These salts form compounds 
with the acetylene and on again subjecting the alcohol to distillation 
they are eliminated and the distillate is obtained pure and absolute. 
Mercuric oxide removes sulphur compounds which are liable to be 
present, since thioaldehydes are almost always formed as a result of 
the action of an acid on calcium carbide. 
Pure absolute alcohol is described as absolutely odorless and 
the product prepared by this method comes as near to being as free 
from having any odor whatever, as any we have ever obtained by 
the methods hitherto described. This fact strongly emphasizes the 
purity of the alcohol made from carbide according to the directions 
we have given. 
The essential reason why calcium carbide is more efficient for 
dehydrating purposes, than quicklime is that it acts upon the water 
* Midland Naturalist, Vol. 1, p. 28. 
