48 
Dr. Thomson's Analysis of 
^ 9-5 grains. A little of this powder being dissolved in muriatic 
acid was precipitated dark blue by prussiate of potash. The 
remainder being mixed with tallow, and suddenly heated in 
a covered crucible, became black, and was attracted by the 
magnet. These properties leave no doubt that the powder 
was peroxide of iron. 
4. The ammoniacal solution had a light blue colour, I there- 
fore neutralized it by muriatic acid, and put into it a polished 
plate of zinc. I obtained a sensible deposit of copper; but so 
small, that I was unable to collect and weis:h it. I estimate it 
at about 0.1 grain. 
5. The white undissolved matter being heated to redness 
weighed 2.1 grains. On examining this matter attentively, I 
found it entirely composed of fragments of quartz crystals 
which had been interspersed through the ore, and had from 
their minuteness escaped my observation. 
6 . From the facility with which the copper dissolved in 
muriatic and sulphuric acids, there could be no doubt that it 
existed in the ore in the state of an oxide. But the red colour 
of the ore made me uncertain whether the oxide was the red 
or the black. I therefore put 100 grains of the ore into a tall 
narrow phial, filled the phial full of water, and then by means 
of a funnel poured a quantity of muriatic acid into the bottom 
of the vessel. The ore was immediately attacked, and the 
solution from the very commencement appeared green. This 
I consider as a demonstration that the copper in the ore was 
in the state of black oxide. Now, black oxide of copper is a 
compound of 100 metal -|- 25 oxygen. So that the 48.6 
grains of copper, extracted from the ore when in the state of 
black oxide, must have weighed 60.75 grains. 
