SULPHURIC. 
grains of distilled water, have the same specific gravity 
at the same temperature ; from whence it follows, that 
the proportion of salt in each was equal. But in the 
last solution the quantity of salt was — of the whole; 
23.6 
28994 
therefore the quantity of salt in the first was 
23.6 
— 159.52 grs. Now of this weight 86 grains were 
alkali; the remainder therefore, which amounts to 
70.52 grains, must be acid. But the quantity of acid 
employed was 79 grains; of this there were 8½ grains, 
which did not enter into the combination, and which 
must have been pure water : 79 parts of acid, of the 
specific gravity 2, therefore contain at least 8, 5 parts 
of water ; and consequently 1o0 parts of it contain 
10.75 parts of water. It only remains now to consider 
how much water sulphat of potass contains. Mr Kir 
wan thinks it contains none, because it loses no weight 
in any degree of heat below ignition, and even when, 
exposed to a red heat for half an hour it hardly loses a 
grain. This is certainly sufficient to prove, at least, 
that it contains very little water; and consequently we 
may conclude, with Mr Kirwan, that 100 parts of sul 
phuric acid, of the specific gravity 2.000, are composed 
pretty nearly of 89.25 of pure acid and 10.75 of water. 
Since there is such a strong affinity between sulphu 
ric acid and water, and since the density of the mixture 
is different from the mean density of the ingredients, it 
becomes a problem of the greatest importance to deter 
mine how much of the strongest sulphuric acid that can 
be prepared exists in any given quantity of sulphuric 
acid of inferior specific gravity, and which consequently 
consists of a determinate quantity of this strong acid di 
luted with water. 
13 
Chap.NV.