Mr. Chenevix's Analysis of Corundum , and of 
respective precipitates to be further examined, before we admit a 
decided affinity between the earths. The quantity of carbonic 
acid also, which must of course combine with the potash, during 
the treatment of the silica by that alkali, should be taken into 
account, in considering the cause of the precipitate. 
The solutions which I used, of all the above salts, were in the 
most concentrate state ; therefore, in the state most favourable 
for showing precipitation, if any had taken place. 
It is not very difficult to account for the appearances that 
deceived Mr. Guyton in his experiments, and for the cause that 
produced them. In one instance, he obtained a precipitate from 
muriate of lime and of alumina, because, in all probability, the 
alumina he dissolved in muriatic acid had been precipitated from 
alum; and alumina, thus prepared, retains a small portion of 
sulphuric acid.* In the next place, it is very likely that his 
solutions were sufficiently concentrate to give a precipitate of 
sulphate of lime. The same was the case with regard to his 
mixture of muriate of strontia with muriate of alumina. As to 
the general conclusion, that barytes has an affinity for lime, 
magnesia, and alumina, which strontia does not appear to pos- 
sess, it is to be explained as follows. Lime often contains a little 
sulphate of lime. Mr. Guyton's magnesia, as well as his alu- 
mina, had probably been obtained from the sulphate ; and we 
are indebted to Mr. Berthollet, for the true nature of many 
similar precipitates. 
* It is somewhat singular, that Guyton should have observed this fact elsewhere. 
See his experiments on the diamond, in the Annales de Chimie. The preparation of 
a barytic salt, by alumina prepared from the sulphate of this earth, had been observed 
by Scheele, in his Essay on the Affinities of Bodies. But that great chemist referred 
the phenomenon to its right cause, viz, to some sulphuric acid remaining in all 
alumina thus prepared. 
