a mineral Substance from. North America. 61 
substance which has been so often mentioned. The precipitate 
therefore produced by the mixture of the two alkaline solutions, 
was a combination of the white matter with oxide of iron, very 
similar to the original ore. 
H. 
The white precipitate, when distilled with four parts of sul- 
phur, remained pulverulent, and, from white, was only changed 
to a pale ash colour. 
Nitric acid was digested on the powder, and, being heated, 
afforded some nitrous gas ; after this, the powder became white, 
and in every respect recovered its original properties. 
I. 
Before I conclude this section, I must observe, that when the 
olive-green precipitates, obtained by prussiate of potash, were 
digested in an alkaline lixivium, they were decomposed; for 
the alkali combined with the prussic acid, and with a small part 
of the white matter ; but the greater part of the- latter remained 
undissolved, in the same white fiocculent state which was noticed 
when the alkaline combinations were mentioned. 
The orange-coloured precipitates, formed by tincture of galls, 
were also decomposed when digested in boiling nitric acid ; and 
the white matter was recovered in its original state. 
§ III. REMARKS. 
The preceding experiments shew, that the ore which has 
been analysed, consists of iron combined with an unknown sub- 
stance, and that the latter constitutes more than three-fourths 
of the whole. This substance is proved to be of a metallic nature, 
by the coloured precipitates which it forms with prussiate of 
potash, and with tincture of galls; by the effects which zinc 
