some of the Substances which accompany it , &c. 343 
Barytes is a much more delicate test than strontia, for sul- 
phuric acid ; and, therefore, barytic solutions were affected by 
quantities of sulphuric acid, which strontia could not render 
sensible. This I have ascertained to be the case : for I have 
obtained copious precipitates, by barytes, in a liquor composed 
for the purpose, wherein strontia did not produce the smallest 
cloud, or show the presence of sulphuric acid. 
A little care and attention are necessary, in preparing the 
earths, which are to be dissolved in the muriatic acid, for these 
experiments ; and, if Mr. Guyton had taken the requisite pre- 
cautions, he would not have been led into error. The object to 
be kept in view is, to free the earth from sulphuric acid ; and, 
if this be obtained, there is not the smallest precipitate or cloud, 
in any of the cases I have mentioned. If any further proof be 
necessary, with regard to the cause of precipitates obtained in 
the manner stated by Mr. Guyton, I may add, that I have re- 
peated his experiments, and have always found the precipitates 
to be sulphate of barytes. 
The general conclusion to be drawn from the observations of 
Mr. Kirwan, already alluded to, is, that barytes has an affinity 
for lime, magnesia, and alumina, upon which earths strontia 
does not seem to have any influence. But these mistakes are to 
be accounted for in the same manner as those of Mr. Guyton, 
viz. by sulphate of barytes being much less soluble than sul- 
phate of strontia, and therefore showing the presence of a smaller 
portion of sulphuric acid, or, in other words, being a much more 
delicate test for that substance. 
With regard to the letter already mentioned as being inserted 
in Nicholson s Journal, and which drew some reflections from 
Yy 2 
