440 
Book II. 
Action on 
barytes. 
Strontian. 
Lime. 
EARTHS. 
with phosphorus, at least no person has hitherto been 
able to form a phosphuret of magnesia. 
There is an affinity between sulphur and magnesia. 
The sulphuret may be formed by exposing a mixture 
of two parts of magnesia and one part of sulphur to a 
gentle heat in a crucible. The result is a yellow pow 
der, slightly agglutinated, which emits very little sul 
phurated hydrogen gas when thrown into water. A 
moderate heat is sufficient to drive off the sulphur *. 
It has no action upon the metals ; nor does it com 
bine, as far as is known at present, with the metallic 
oxides, unless some intermediate substance be present. 
Neither does magnesia combine with the alkalies. 
There seems to be little affinity between magnesia 
and barytes ; at least no mixture of the two earths is 
fusible in the strongest heat which it has been possible 
to applyf. Muriat of magnesia, indeed, and muriat of 
barytes, occasion a precipitate ; but the nature of this 
precipitate has not been examinedf. 
Mr Kirwan has shown that there is but little affinity 
between strontian and magnesia. They do not melt 
when exposed to a strong heat, at least when the stron 
tian exceeds or equals the lime . 
Equal parts of lime and magnesia, mixed together, 
and exposed by Lavoisier to a very violent heat, did not 
melt; neither did they melt when Mr Kirwan placed 
them in the temperature of 150° Wedgewood. —The 
following Table, drawn up by Mr Kirwan from his 
own experiments, shews the effect of heat on these two 
earths mixed together in different proportions. 
t Lavoisier, Mem. Par. 1782. 
F Fourcroy, i. 165. 
Irisb Tranc. v. 246, 247. 
Morveau, Ann, de Chim. xxxi. 253.