[ M ] 
mixture was found to have melted, and form’d a 
fmooth, uniform lump. The platina, which had 
funk to the bottom, being feparated from the mix- 
ture by walking, prov'd of the fame appearance as at 
firfl, tho’ a little deficient in weight. 
3. The experiment was repeated with what is call’d 
the regal ceine?it> a let's fufible mixture, compos'd of 
common fait and colcothar each one part, and four 
parts of powder’d red bricks. An ounce of platina, 
furrounded, as above, with fix ounces of this com- 
petition, and cemented in a clofe-luted crucible with 
a red heat, for twenty hours, was flill found unalter'd 
in appearance, tho’ there was fome deficiency, as be- 
fore, in the weight. 
Remark. The marine acid, when thus detaind 
in the fire by the combination of other bodies, till 
ftrongly heated, and then fet at liberty in the form of 
fume, difl'olves or corrodes all the known metallic 
fubflances, gold alone excepted. As the platina, in 
thefe experiments, retain’d its original polifh’d fur- 
face, without any mark of corrofion j it was prefumd, 
that this mineral likewife had refilled the marine 
fumes ; and that the deficiency was owing to fome of 
the fmaller grains having been wafh’d off, along with 
the ponderous colcothar or metallic matter of the vi- 
triol ; an accident not eafily avoided. 
4. Platina was therefore treated with mercury- fub- 
limate, a combination of the highly-concentrated ma- 
rine acid with a volatile fubfiance, wdiich in a proper 
degree of heat it readily forfakes to unite with other 
metallic bodies. An ounce of platina was fpread 
upon three ounces of powder’d fublimate ; the glafs 
cover’d, and fet in fand : After a moderate fire for 
fome 
