on the CompojiUon of James’s Powder . 261 
The manner in which air and fire a£t upon the antimonial 
calx and phofphorated lime, 1 (hall venture to conjecture. 
It is probable, that the calx of antimony and phofphorated 
lime combine with each other. 1. Becaufe it requires the ap- 
plication of heat and air for a (hotter fpace of time to feparate 
the fulphur from a given quantity of antimony mixed with 
bone-afhes than to produce this effedl on antimony by itfelf : 
nor can the fpeedy calcination of antimony, with bone-afhes be 
explained by fuppofing that the antimony can then bear more 
heat without melting ; for the difference in the degree of heat 
applied in the two cafes is not, apparently, fufficient to account 
for the difference of the times required for defulphu rating the 
antimony. 2. Becaufe it appears, that heat, applied to anti- 
mony in a confiderable variety of degrees, and air for various 
fpaces of time, formed a calx very different in colour, fufibi- 
lity, and other chemical qualities, from that produced by cal- 
cining this metallic fubftance with bone-afhes. The ft'rongeft 
confirmation, perhaps, of the opinion that the antimonial calx 
and phofphorated lime are chemically united together is, that, 
however long the calcination of the antimony and bone-afhes is 
continued in the open veffel it will only produce precifely the 
fame fubftance, with refpedft to chemical properties, that is 
produced the moment the fulphureous fumes ceafe. 
But why is a fnow-white powder produced by expofing a 
mixture of calcined antimony and bone-afhes to air and fire for 
a due length of time, and then applying a greater degree of fire 
Hi clofe veffels, whereas no fuch white powder is formed by a 
mixture of any calx of antimony and bone-afhes, expofed to any 
degree of fire in clofe veffels, without previous expofure to fire 
and air ? The reafon may be, that in order that .the calx (homd 
unite with the phofphorated lime, it muft be calcined to one 
Vol. LXXXI. Bbb certain 
