absolute Alcohol, and the Composition of'Proof-Spirit." 127 



The proportions of absolute alcohol and water mixed were 

 as under, all by weight. Temperature of room 60° F. Baro- 

 meter 29-832. ' 



First mixture. — 588 grs. alcohol + 612 grs. water, being in 

 the proportion of 49 grs. alcohol + 51 grs. water. 



Second mixture. — 594 grs. alcohol + 606 grs. water, being 

 in the proportion of 49| grs. alcohol + 50| grs. water. 



After twenty-four hours, the bottles having been frequently 

 shaken, the specific gravities of both mixtures were taken, 

 with all the precautions detailed in the experiments on ab- 

 solute alcohol: and in order to observe if the full condensa- 

 tion was gradual and required time for its completion, the 

 mixtures were allowed to stand, with occasional agitation, for 

 a further period of twenty-four hours, when the liquids were 

 again weighed. The results \^'ere as follows : — 



At 24 hours, temperature of room 60° F., barometer 29"630. 

 At 48 hours, temperature of room 60° F., barometer 29"550. 



First Mixture. Second Mixture. 



I. -920361 \ after standing I. -911)297") after standing 

 II. -920358/ 24 hours. II. -919297/ 24 hours. 



III. .920361 /^^^"■f^"^^"^ III. •919307/^^^^\^^^"^"^S 

 \^ 48 hours. )^ 48 hours. 



Mean -920360 Mean -919300 



It thus appears that both liquids attained a fixed specific 

 gravity within the first twenty-four hours. 



If we now express the preceding results by measure, and 

 make the proportion of alcohol a constant quantity in the two 

 mixtures, we have — 



Alcohol and water Alcohol and water S|)ec. gravity 



by weight. by measure. of the mixtures. 



Alcohol. Water. Alcohol. Water. 



49 + 51 \in the pro-/ 100 + 82-62105 -92036 



49^ + 50^J portion of 1^100 -h 80-98470 -91930 



Difference . . 1-63635 106 



Dividing the difference of the quantities of water by the 

 difference of specific gravity, we get -015437, the mean quan- 

 tity of water corresponding to each unit of difference in the 

 specific gravities. But the difterence between the specific 

 gravity of proof-spirit and -91930, one of the observed specific 

 gravities, is 54; tlierefore we have 54 x -015437 = -8336, the 

 <]uantity of water to be added to the spirit of that specific 

 gravity to form proof-spirit, as follows : — 



