On the Assay of Minerals ly means of the Blowpipe. 443 
periment: that is to say, whether they are easy and rapid, or 
slow and dificult, and simple or compound : they are simple, 
when one phenomenon only i is presented, as in the fusion of 
compact feldspar; compound, when several are manifested ; 
and the latter may be simultaneous, like the smell, flame, smoke, 
and carbonization of coal; or successive, like the divis on, swell- 
ing, and fusion of borax, 
The change undergone by a mineral may be strong or feeble, 
as the greater or smaller part of it is attacked. Universal or 
partial : universal, when it attacks all the particles of a mineral, 
like native antimony, which is totally converted into smoke; and 
partial, when it affects only certain particles, as in antimonial 
silver, when the antimony is reduced to smoke, while the silver 
remains fixed. 
_The way in which minerals act is various, according to the 
methods employed. 
When the assay is made with additions, we must consider 
the nature of the substance added in order to facilitate the fu- 
sion of the mineral. Among the fluxes, some operate the reduc- 
tion and others the oxidation of the metal, as nitre. 
The fluxes employed are used either dry, by mixing them 
with the mineral after reducing both into powder, or by melt- 
ing the mixture and forming a paste, which is exposed to the 
action of the flame. Before employing fluxes, it is proper to 
take the water of crystallization from such as contain it. 
The fluxes most in use are, 1. Mintum, for earthy substances. 
2. Fluor Spar, which is a very good flux for gypsum, with 
which it forms an enamel. 3, Gypsum is reciprocally an ex- 
cellent flux for fluor spar. 4. Borax, which is often employed 
indiscriminately for earthy and metallic substances, and which 
frequently acts as a reductive flux: but before employing it we 
ought to take care to reduce it to glass. 5. Nitrated Borax, i. e. 
the superabundant soda of which is saturated with nitric acid: 
this is one of the best fluxes, particularly for metalliferous sub- 
stances. 6. Carbonate of Soda, which is advantageously em- 
ployed with siliceous substances. 7. Carbonate of Potash. 8. 
Microcosmic Salt, which is very efficacious. 9. Glass of Phos- 
phorus, i. e. the phosphoric acid reduced to the vitreous state. 
10. Mitre, which is an excellent assay for inflammable sub- 
stances, and a powerful flux for metallic substances. 
With the exception of nitre and borax, we may employ the 
various fluxes on all kinds of studs; but with those which pos- 
sess the property of detonating with charcoal we must use the 
small platina spoon. 
The reductive fluxes are those which take u up the oxygen from 
minerals, or which prevent it from combining with them. 
The 
