38 Dr. fordyce’s Method of 
This may eafily be tried by taking common green or blue 
vitriol, diffolving an ounce in three ounces of water by 
boiling, letting them ftand to cool, and filtering the folu- 
tion. If this folution be expofed to the air it will remain 
perfect; but if we drop a drop or two of it into a wine 
glafs full of water, in a few minutes the tranfparency of 
the water will begin to be difturbed, and the metal in a 
fhort time will fall down, in a red powder if it be iron, in 
a blue powder if it be copper. 
An hundred grains of the ore is fufficient to give the 
copper contained to one hundred part; if greater accu- 
racy be required 1000 grains may be ufed. 
The mixture of nitrous and muriatic acid is the molt 
* 
proper acid menjlruum for copper ores, muriatic acid dif- 
folving moll readily the calces of metals, and nitrous 
acid when they are in their metallic form ; a metal in its 
metallic form being a compound of a pure calx and a fub- 
ftance, which has been called inflammable air, but which 
is an oil found out by stahl to exift in metals, and which 
we would call the oil of metals. The nitrous acid de- 
compofes this oil, at the fame time that it adds on the calx 
itfelf, and leaves it alfo to be added upon by the muriatic 
acid. 
When copper is combined with fulphur in an ore, it is 
in its metallic form ; in diffolving in an acid its oil rifes 
m 
