46 MIDLAND NATURALIST. 
in two stages: CaC,+H,O=Ca0+C,H,; CaO-+H,O=Ca(OH).. 
- In the first stage of the reaction acetylene and calcium 
oxide are formed; and the calcium oxide then unites with more 
water producing calcium hydroxide. Thus for every molecule of 
carbide used there are two molecules of water acted upon. Using 
ordinary unslaked lime we have an agent which is theoretically 
one-half as efficient as carbide and practically never even half as 
efficient, since its reaction is the same as the one taking place in the 
second stage when carbide is used, consequently it has the dis- 
advantage of not being as active in uniting with water as is carbide, 
and since it absorbs a great deal of alcohol, thereby the distillation 
from the residue becomes very slow and incomplete. 
In an experiment using two liters of alcohol having a specific 
gravity of .832 or about 90 per cent purity, we obtained 1400 CC 
impure alcohol such as could be used for dehydrating in methods of 
histological technique,—the only piece of apparatus used being an 
ordinary bottle containing the mixture. By distilling the residue 
or slag remaining after these 1400 cc of alcohol had been decanted, 
nearly 400 cc more of alcohol absolutely free from water was ob- 
tained, thus making the yield almost quantitative. To this dis- 
tillate were added a few grams of dried mercuric nitrate and some 
silver nitrate. The mixture was then allowed to stand about a day 
in a warm place till all the acetylene and other compounds, which 
are formed due to the impurities in the carbide, were acted upon. 
In order to be sure that all the acetylene has combined with the 
mercury and silver salts, some of the clear liquid was decanted and 
tested with a small portion of finely powered silver nitrate. Any 
precipitate or dark coloration which formed on standing indicated 
the presence of impurities, and necessitated the addition of more 
mercury and silver salts. 
When all the impurities from the carbide were removed, the 
liquid, after decantation or filtration from the precipitate, was dis- 
tilled and found to have a specific gravity of .7876 at 25? C. ora 
purity of 99.8 percent. The distillate had hardly any odor or a 
very slight but pure ethereal one, and was practically free from 
any foreign substance whatever. It is always necessary to free the 
liquid from any of the'precipitates of silver or mercury carbides 
formed by the action of the acetylene on the purifying salts, for 
there is danger of their exploding or decomposing when the last 
portions of the alcohol are distilled.* 
It required several days to effect the dehydration, and 550 
grams of calcium carbide was used. The ct may, how- 
