THE PHYSICAL PROPERTIES OF METHYL-ALCOHOL. 515 



From either of the two series it should be possible theoretically to calculate 

 the quantities of air retained by the liquid ; but a little reflection, based on 

 the requisite formulae, shows that the experimental data do not afford the 

 necessary degree of precision for this purpose. 



Assuming that at any of the three volumes all the air is in the vapour, and 

 taking x as representing its volume in c.c. at f, and 1 mm.'s pressure, we have, 



First Series (16°). 



By combining (1) and (3) .... x = 306 



(2) and (3) . . . . a; = 266 



Mean, . . x = 286 



From this mean and by equation p = - +p Q , where p stands for the total pres- 

 sure as observed, and p for the partial pressure of the alcohol vapour, we have 



From (1) (2) (3) 



p = 80-0 78-8 790. 



Second Series (11°). 

 By combining (2) and (3) we have 



p = 55-19 and x = 551'2 c.c. 

 From (1) and (3) we have 



_p = 57'60 and a: = 322-2 c.c. 

 From (1) and (2) we have 



p = 58-73 and x = 300-4 c.c. 



From these results we clearly saw that a sufficient exactitude for p could 

 not be obtained in this manner, and we therefore fell back upon the old method 

 of " boiling out " the specimens to be operated upon in their respective tubes 

 before shutting them up. From a large mass of notes we extract the follow- 

 ing :— 



Two alcohols, A and B, were mixed to produce about 300 c.c. of "D." 

 The specific gravity found was such that, according to our present alcoholo- 

 metric tables, the percentage of absolute alcohol was 98*66. # Four distilla- 

 tions over anhydrous sulphate of copper brought down the specific gravity so 

 that it now corresponded to 98-81. This alcohol was distilled by itself, and 

 the distillate collected in two approximately equal fractions. Their specific 



gravities, reduced to per cents., corresponded to QQ.k 9 qo.qn; as we now see '> 

 at the time we took them both as representing absolute alcohol. 



* We propose, for the convenience of trie reader, to quote the results in this manner; at the time 

 we had, of course, to go by the specific gravity as a mere index of strength. 



