'238 



PHILOSOPHICAL TRANSACTIONS. 



[anno 17 82. 



of 251Q.75 gr. of oil of vitriol, whose specific gravity was I.8I9, with 180 of 

 water, I found its density 6 hours after 1.77 1 ; hut after 24 hours it was I.798; 

 and hence, according to the reasoning in the former paper, the accrued density 

 was at least .064, instead of .045, as I had formerly found it. But by using oil 

 of vitriol still more concentrated, whose specific gravity was 1 .8846, I was en- 

 abled, by a similar train of reasoning, to make a still nearer approximation, and 

 found that the accrued density of oil of vitriol, whose specific gravity is 1.81 9, 

 amounts to 0.104; and consequently its mathematical specific gravity is 1.715. 

 Now 6.5 gr. of this oil of vitriol contained, as I before found, 3.55 of mere acid, 

 and the remainder water, and the weight of an equal bulk of water is 3.79 gr. ; 

 then subtracting from this the weight of the water that enters into the compo- 

 sition of the oil of vitriol, it will be found, that the weight of a bulk of water, 

 equal to the acid part, is 0.84, and consequently the specific gravity of the pure 

 and mere acid part is 4.226. On this ground, and constantly allowing the mix- 

 tures to rest at least 12 hours, till the oil of vitriol was diluted with 4 times its 

 weight of water, and then often only 6 hours, before their density was examined, 

 I constructed the table hereto annexed; the temperature of the room being con- 

 stantly kept between 50 and 6o°; and the column of acid being always 6 12.05. 



