358 RELATIVE ATTRACTIONS OF 
total quantity of diluted acid remaining in the 
dish ; the per centage of real acid in which being 
71.53 nearly ; acid of this strength is of about the 
sp. gr. 1.814. 
The temperature of that particular part of the 
room in which this air pump experiment was 
made, was regularly registered three times a day, 
whereby it was perceived that from the 22nd Sep- 
tember to the 6th October, the temperature never 
ran higher than 65°, and from the 6th October 
to the 13th, not higher than 57°; from the 13th 
to the 27th, it was also frequently as high as 57° ; 
hence it follows, that an evaporating force of 0.61 
of an inch of mercury, has, in the instance of this 
experiment, been sufficient to concentrate the 
acid down to the sp. gr. 1.8145; and, conse- 
quently, that acid-of such strength is capable of 
drying a vacuum when the temperature does 
not exceed 57°. 
EXPERIMENT II. 
On the morning of the 3rd October, 1837, I 
put into two light evaporating dishes, of 24 inches 
in diameter, 10 grains by weight of diluted sul- 
phurie acid, sp. gr. 1.135; and the dishes, after 
being moved about until the acid had spread itself 
