358 Professoggy W. B. and R. E.. Rogers 
decomposing the chloride of calcium and liberating hydrochloric 
acid. 
It is evident therefore that the application to Rose’s apparatus 
of a heat sufficient to expel the carbonic acid from the solution, is 
entirely inadmissible, whichever solvent we employ. It is scarce- 
ly necessary to add that this remark is also applicable to the ap- 
paratus of ipl that of Will and Fresenius, and that of inate 
_man and Marchan 
As in a recent memoir of the two chemists last named, they 
express a preference for sulphuric acid in experiments of this kind, 
it becomes important to our enquiries to ascertain whether the 
sulphuric solution produced in such case, would retain enough 
carbonic acid to make the boiling process necessary. We there- 
fore introduced into the bottle one hundred grains of carbonate 
of lime, and poured upon it a sufficient amount of sulphuric acid, 
diluted with an equal bulk of water, to prevent the formation of 
a thick magma. Notwithstanding the large excess of acid, and 
frequent agitations of the liquid, the action towards its close was 
extremely slow, so that at the end of four hours, a slight crepl- 
tation could be heard on stirring the mixture. When this had 
entirely ceased, the liquid was heated in the graduated tube as 
above described.. As the temperature approached boiling, ¢al- 
bonic acid was evolved, and at the close of the process, the vol 
ume of this gas collected was upwards of four tenths of a cubic 
inch. A similar result was obtained with several other carbo- 
nates and sulphuric acid. 
We are therefore justified in affirming, that the solution or mix- 
ture formed in this process, whether sulphuric or hydrochlori¢ 
acid be used, always contains an amount of carbonic acid 00 
great to be overlooked in accurate research; that this carbonic 
acid cannot be expelled by a heat below biting; and that such a 
temperature cannot be applied to the liquid while in the appara 
tus, without entirely vitiating the result. We therefore attach 
much importance, in cases of nice research, to the separate heat 
ing of the liquid, and we believe that with proper care the process 
for that purpose above described, will give the amount of residu- 
ary carbonic acid with all needful exactness. 
The critical nature of the researches in which we proposed to 
employ the above mentioned instruments and processes, made it 
necessary, before entering on the main objects of investigation, to 
