3. It appears therefore that the aggregate of the analytical results would indicate 79 grs. of ignited sulphat of barytes, instead of the 74 grs. obtained by a single direct operation. This difference I apprehend to be in a great degree owing to my estimate of the proportion of acid in sulphat of alumine being over-rated, from the circumstance of not having been able to obtain a neutral sulphat of alumine in the experiment just relaxed from which that estimate was deduced.
§ XVI. Silica.
I. During the various solutions of the residue in acid, I had repeatedly observed that, besides the selenite, (the solution of which
