SULPHURIC ACID FOR WATER. 385 
the furnace in which the sulphur is burnt, suffi- 
ciently high to keep up the combustion, when he 
attempts to burn only a minimum of sulphur ; and, 
not having (in many instances) other means of 
preserving the requisite temperature, he is reluc- 
tantly urged to burn more sulphur than circum- 
stances render him capable of converting into, 
and collecting in the state of, sulphuric acid. 
So far, then, I have shown that when the floors 
of the chambers are covered only with water, or 
dilute acid, there is substantial reason why less 
sulphuric acid should be collected from a given 
quantity of sulphur in cold weather than in warm: 
and, when we take into consideration that the 
acid on the floors of the chambers is seldom very 
dilute ; but that it is frequently allowed to be of 
such strength as to have the sp. gr. 1.45 or 1.50, 
we find that there is additional reason why cold 
weather should be objectionable. On reference 
to the table of the results of my experiments, we 
see that at the temperature of 36°, and at the 
pressure there stated, the acid was only capable 
of being concentrated till its per centage was 58.1, 
=sp. gr. 1.6405, and we may conceive that if the 
evaporating force of space at the temperature of 
36°, was just balanced by the attraction of acid 
3.C 
