226' 
Dr. Thomson on some of 
VII. Chromiron Ore. 
In my “ First Principles of Chemistry," vol. ii. p. 55, I 
express an opinion, that this mineral is a compound of 2 
atoms brown oxide of chromium and 1 atom peroxide of 
iron. The facts stated in this Paper, showing that this opi¬ 
nion was ill founded, it became necessary to endeavour to 
determine the composition of the mineral by experiment. 
The following table exhibits the result of all the analyses 
of this mineral that have come to my knowledge. 
ii 
M 
u 
a 
p 
< 
> 
* 
I' Laugier. 
» 
H 
0 
A 
P. 
■t-f 
§ Seybert. 
• 
Pi 
n 
?H 
CO 
II Berthier. 
II Berthier. 
Thomson. 
Thomson. 
Green oxide of chrome 
Peroxide of iron - - 
Alumina - - - - 
Silica ----- 
White matter - - - 
Moisture - - - - 
43 
347 
20-3 
2-0 
53 
34 
11 
I 
55 'S 
33 
6 
2 
39-514 
36-004 
13-002 
10-596 
51-562 
35-140 
9-723 
2'90I 
36 
37-2 
21-8 
5 
51-6 
37-2 
97 
2-9 
47-92 
34-08 
11-76 
I-06 
4-18 
1 
52-45 
24-33 
17-80 
2* * * § 20 
I-61 
100 
99 
96-5 
99-116 
99-326 
100 
ioi’4 
100 
98-48 
* Jour, de Mines, x. p. 521. The specimen was sent from the departments of 
the Var. No description is given. Sp. gr. 4'0326. 
f Philosophical Magazine, xxiv. 7. The specimen was from the Uralian moun¬ 
tains. Sp. gr. 4'0579. 
J Beitrage, iv. 132. The specimen was from Styria. Sp. gr. 4*5. 
§ Silliman’s Jour. iv. 321. The specimen was from the Bare Hills, Baltimore. 
Sp. gr. 4-0639. 
^ Ibid. p. 323. The specimen was from Chester, Pensylvania. 
II Ann. de Chim. et de Phys. XVII. 55. The first specimen from Isle de Vache, 
near St. Domingo; the second from the neighbourhood of Philadelphia. Obvi¬ 
ously the same as Seybert’s second specimen. 
