378 RELATIVE ATTRACTIONS OF 
paper on “‘ water as a constituent of salts,” pub- 
lished in the Transactions of the Royal Society of 
Edinburgh, vol. xiii, part 1, and in the London 
and Edinburgh Philosophical Magazine, for May, 
1835, it would be inferred that a low temperature 
would not be capable of concentrating sulphuric 
acid to any considerable strength ; for, he therein 
alludes to having observed a close approximation 
to the sp. gr. 1.78, in concentrating a dilute acid 
at a temperature not exceeding 300°; and he 
states that in one experiment, a small quantity of 
dilute acid was found to concentrate down to 
three atoms of water to one anhydrous acid ( =sp. 
gr. about 1.66,) at a temperature not exceeding 
212°. My experiments prove that so low a tem- 
perature as 48°, and exposure to anhydrous air, 
are enough to concentrate the acid to the sp. gr. 
1.7071, if sufficient time be allowed; and a tem- 
perature of 55°, to the sp. gr. 1.76. 
The results arranged in the table, will, I believe, 
be found, at least, near approximations to the 
truth : and, while they point out to us, in seven 
individual cases, the particular strengths of acid 
whose attractions for water counterbalance the 
evaporating force of anhydrous space, under the 
several circumstances ; they also enable us to form 
