absolute Alcohol, and the Composition of '^Proof-Spirit." 125 



From these experiments it would appear that sulphate of 

 copper, Avhen deprived of water, is not so effective as quick- 

 lime in removing the last traces of water from alcohol. 



It was observed, however, that in general the specific gra- 

 vity of the alcohol gradually increased, probably from its hy- 

 grometric property, by which it absorbed a minute quantity 

 of moisture from the air on being transferred from one bottle 

 to another ; and thinking consequently that a small quantity 

 of moisture might have been abstracted from the atmosphere 

 during the distillation (which was conducted in the usual 

 way), and the specific gravity thus slightly increased, I con- 

 sidered it desirable to make another experiment in which this 

 source of error should be guarded against, by conducting the 

 distillation as much as possible out of contact with the ex- 

 ternal air, and proceeded as follows. 



The different portions of alcohol before obtained were 

 mixed together, when the specific gravity was found to be 

 "7947; this alcohol was again digested at a temperature of 

 about 150' F. for fourteen days with quicklime, previously 

 heated to redness, as in the former experiment ; it was then 

 slowly distilled out of contact with the external atmosphere 

 by means of a tube which passed from the condenser through 

 a cork into the bottle in which it was to remain (the tempe- 

 rature of the water-bath was 175° F.), and the first tenth 

 part was put aside as possibly containing a minute quantity of 

 water; the remainder was then distilled off at 178° to 1B0° F. 



This alcohol was quickly transferred to a dry retort and 

 redistilled in a similar way (heat of water-bath 172° F.) ; the 

 first tenth part was put aside, and the remainder kept as 

 being pure anhydrous alcohol, or as free from water as it is 

 possible to obtain it by this process. The specific gravity was 

 taken the next day with all the precautions before mentioned, 

 the alcohol being also kept during the time of transference 

 as much as possible out of contact with humid air, when the 

 results of four trials were as follow : — 



Temperature of room 60° F. Barometer 29-810. 



I -793836 



II -793806 



III -793798 



IV -793804 



Mean . -793811 



A portion of this alcohol was subsequently digested with 

 quickUme for tln'ce months, it was then distilled, and its 

 sj)ecific gravity Mas found to be exactly the same as before. 



We may therefore conclude with considerable certainty 



