PHYSICAL anv LITERARY. 183 
THE fame white powder is alfo formed 
when fpirit of vitriol is added to a calca= 
rious earth diffolved in any other acid; 
the vitriolic expelling the other acid, and 
joining itfelf to the earth by a ftronger 
attraction; and upon this account the 
magnefia of fea~water feems to be different 
from either of thofe defcribed by Moffman, 
He fays exprefsly, that the folutions of 
each of his powders, or, what is equivalent, 
that the liquors from which they are ob- 
tain, formed a coagulum, and depofited a 
white powder, when he added the vitri- 
olic acid *; which experiment J have often 
tried with the marine bittern, but without 
fuccefs. ‘The coagulum thus formed in 
* the mother of nitre may be owing to a 
quantity of quick-lime contained in it; 
for quick-lime is ufed in extracting the 
falt-petre from its matrix, But it is more 
difficult to account for the difference be- 
_ tween Hoffman’s bittern and ours, unlefs 
_ we will befatisfied to refer it tothis, that 
he got his from the waters of falt {prings, 
which 
‘dl Hoff, Op, ‘FE: 4 Pp. 480 & 500» 
