192 An Analysis of two Mineral 
tallic copper on the iron plate. 6. Digest copper 
filings in the liquor in which iron filings have been 
previously digested; separate the copper filings, and 
now let a piece of bright iron be put into the liquor; 
in this case, copper is deposited on the surface of 
the iron in its metallic state. 7. Put a small piece 
of sulphat of argill into a glass of the solution, after 
fresh iron filings have been digested with it ; a white 
stratum forms at the bottom of the glass, but, after 
some time, it is re-dissolved and the liquor resumes 
its transparency. 8. Put a little oxygenated muriat 
of mercury into a glass of the hepatised solution; 
as it dissolves, a white matter collects on the sides, 
and falls to the bottom, of the glass. g. Infusion 
of galls, after the fresh iron has been digested with 
the solution, precipitates the iron of a dark colour; 
still the prussiat of potash does not become turbid.— 
From al] these facts it is clear, that, as the iron com- 
bines with the sulphur of the hepatic gas, a peculiar 
substance is formed and dissolved in the water, which 
has hitherto been unnoticed by chemical writers, as 
far as has fallen within my information. That this 
substance is contained in the waters of the spring un- 
der our present examination seems fully established, 
by the concurrent €évidence of so many phenomena 
in which they completely coincide. Compare 111. 
LOG,2.1Vs 15 25 .Bo\hy OG: 
