250 
MR. FOWNES ON THE VALUE IN ABSOLUTE ALCOHOL 
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 
gravity difficult and troublesome when the temperature of the room is either above 
or below C0°. The same remark applies to the mixtures of alcohol and water ex- 
tending over more than half the Table, the most minute precautions regarding tem- 
perature 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 2975 
inches. Lastly, when analysed by combustion with oxide of copper, it yields numbers 
representing the proportions of carbon and hydrogen present so closely agreeing with 
those required by theory, as to leave no doubt of its purity and freedom from all ad- 
mixture. 
The contraction of volume suffered by various mixtures of alcohol and water may 
be rendered obvious by comparing the actual specific gravities of such mixtures with 
the calculated mean specific gravities. In the accompanying Plate (XIII.), in which 
the vertical lines represent the per-centage of alcohol by weight, and the horizontal 
lines the specific gravities, the calculated mean specific gravities of the mixtures are 
seen to form a straight diagonal line from corner to corner, while the actual specific 
gravities form an irregular curve with upward convexity, rising quickly to near its 
maximum deviation at 30 per cent., running nearly parallel with the other line to 50 
per cent., and thence declining until it reaches the extremity of the scale. 
University College , 
June 7th, 1847. 
