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XIX. On the PrejMration of absolute Alcohol, and the Com- 

 position of " Proof-Spirit." By Mr. Joseph Drink- 

 water. [Communicated by Professor Graham.)* 



^ I ''HE following experiments were undertaken, principally, 

 with a view to determine the relative proportions of an- 

 hydrous alcohol and water in revenue proof-spirit, for which 

 purpose it was necessary to procure alcohol in its absolute or 

 pure state. 



The processes employed were as follows : — 



Carbonate of potash was exposed to a red heat to deprive 

 it of water, and when sufficiently cool was pulverized, and 

 added to ordinary alcohol of specific gravity -850 at 60^ F. 

 till it ceased to dissolve any more ; the whole was then al- 

 lowed to digest twenty-four hours, being frequently agitated, 

 when the alcohol was carefully povu'ed off. 



As much fresh-burnt quicklime as was considered sufficient 

 when powdered to absorb the whole of the alcohol, was in- 

 troduced into a retort, and the alcohol added to it ; after digest- 

 ing forty-eight hours, it was slowly distilled in a water-bath 

 at a temperature of about 180° F. 



The alcohol thus obtained was carefully redistilled, and its 

 specific gravity at 60° F. was found in two experiments to 

 be '7946 and •7iM7 ; agreeing very nearly with the determi- 

 nation of Rudberg, which has been adopted by Gay-Lussac 

 and others, viz, '7947 at 59° F. 



It may be proper to state that the specific gravity was 

 taken with a stoppered bottle, which was always counter- 

 poised by another empty bottle of the same glass and form, 

 placed in the opposite pan of the balance ; the capacity of 

 the weighing bottle at 60° F. was exactly lOOO'Ol grains of 

 distilled water ; and it was found on trial that this bottle 

 could be repeatedly filled with the same liquid with no greater 

 variation than one or two hundredths of a grain. 



The temperature of the room in which these experiments 

 were made was always brought to 60° F. ; and the thermo- 

 meter used was a standard instrument by Newman, and ex- 

 tremely sensitive (being graduated to one-tenth of a degree) ; 

 on being plunged into the weighing bottle filled with alcohol 

 it displaced about 4^ grains of that fluid; this portion was 

 replaced from the stock quantity (brought at the time to the 

 prcjpcr temperature) by means of a pipette. 



With a view however to discover whether it were possible 

 by means of lime to abstract any more water from the alcohol, 

 the retort was again filled with fresh-burned and pulverized 



• Conimunicatcd by thp (Jhemical Society: having been read June 21, 

 1847. ' 



