Mr GRAHAM'S Account of the Formation of Alcoates. 177 



taining three or four ounces of commercial alcohol is made to 

 rest upon the lime : the whole is placed upon the plate of an 

 air-pump, and covered over by a low receiver. Exhaustion is 

 continued till the alcohol evinces signs of ebullition, but no far- 

 ther. Of the mingled vapours of alcohol and water which now 

 fill the receiver, the quicklime is capable of combining with the 

 aqueous vapour only, which is therefore quickly withdrawn, while 

 the alcohol vapour is unaffected. But as water, unless it has an 

 atmosphere of its own vapour above it, cannot remain in the al- 

 cohol, more aqueous vapour rises. This vapour is likewise ab- 

 sorbed, and the process goes on till the whole water in the alco- 

 hol is withdrawn. Several days are always required for this pur- 

 pose, and in winter a longer time than in summer. The follow- 

 ing cases exhibit the rate, according to which the water is with- 

 drawn. The first experiment was made in summer. Four ounces 

 of alcohol of the specific gravity 0.827 were concentrated. The 

 specific gravity was taken every twenty-four hours, and the fol- 

 lowing series of results obtained : 



0.827 

 0.817 

 0.808 

 0.802 

 0.798 

 0.796. 



In this case the whole water was withdrawn in five days, but 

 occasionally a period somewhat longer is required, although it 

 rarely exceeds a week. In winter the alcohol generally requires 

 to be exposed to the lime for a day or two longer than in sum- 

 mer. The following rate of concentration was observed in one 

 case in winter, the quantity of alcohol and other circumstances 

 being the same as in the former experiment : 



VOL. XI. PART I. Z 



