VALUE IN ABSOLUTE ALCOHOL OP SPIRITS. 
109 
pered bottle, and heated for some time to a temperature 
above its boiling point. 
In this manner, each alternate number in the table (each 
even number) was obtained by direct experiment; the 
others were then interpolated. When completed, the table 
was examined by various methods calculated to test its ac- 
curacy, but no error of sufficient magnitude to limit its 
usefulness was detected. 
The absolute alcohol employed in these experiments was 
prepared in the following manner: — the strongest rectified 
spirit was agitated with half its weight of carbonate of 
potash, deprived of water of crystallization, and left in con- 
tact with the salt some days. It was then decanted upon 
half its weight of powered quicklime, made from black 
marble, contained in a metal still, which could be perfectly 
closed. The mixture of spirit and lime was retained in a 
warm situation for a week or thereabouts, and then dis- 
tilled by means of a water-bath. By this treatment the 
specific gravity of the alcohol was generally reduced to 
.796, or even below, and by a repetition of the process of 
digestion v/ith powdered lim.e and re-distillation, the last 
traces of water were removed. In this manner, without 
difficulty, the very considerable quantityof absolute alcohol 
required for the experiments was procured. 
Absolute alcohol thus obtained, has the specific gravity 
.7938 at 60° Fahr. ; it is extremely expansible by heat, 
which renders the determination of its exact specific gravi- 
ty difficult and troublesome when tlie temperature of the 
room is either above or below 60°. The same remark ap- 
plies to the mixtures of alcohol and water extending over 
more than half the table, the most minute precautions re- 
garding temperature being necessary to avoid serious errors. 
In a glass retort, containing pieces of copper foil, absolute 
alcohol boils at 177° Fahr., the barometer standing at 29.75 
inches. Lastly, when analysed by combustion with oxide 
