REPORT ON CHEMISTRY. 
485 
The last two exhibit the composition of the pure mineral = 
• .V. 
(Pb -f Cl) + 3 (3 Pb + P) ; the others are represented by 
Pb + Cl 
Ca + F 
• • 
+ 3P+3 
3 Pb 
3 Ca 
Hedyphan he shows to be the same mineral in which a portion 
of the phosphoric is replaced by arsenic acid. 
An observation of Mr. Harcourt in regard to the phosphates 
of lead has become highly interesting since the discovery of 
vanadic acid in minerals having the same form. He found the 
orange phosphate to contain 1‘2 per cent, of chromate of lead. 
With which of the other electro-negative constituents of these 
••• ••• 
minerals are Cran \ isomorphous ? 
Octohcedral minerals .—Abich, the grandson of the celebrated 
Klaproth, has investigated the composition of several octohae- 
dral minerals, the result of which has been to show that all 
these minerals have a similar atomic constitution, according 
perfectly with the views of Mitscherlich in regard to bodies 
which assume the same crystalline form. Their composition is 
as follows : 
Locality. 
Alu¬ 
mina. 
Protox¬ 
ide of 
Chro¬ 
mium. 
Perox¬ 
ide of 
Manga¬ 
nese. 
Perox¬ 
ide of 
Iron. 
Magne¬ 
sia. 
Protox¬ 
ide of 
Iron. 
Oxide of 
Zinc. 
Silica. 
0 
Spinell from Aker ... 
68-94 
25-72 
3-49 
2-25 
———- Ceylon.. 
69-01 
1-10 
26*21 
0-71 
2*02 
Pleonast from Ural... 
—--■ Mont- "I 
65-27 
17*58 
13-97 
2-50 
66-89 
23-61 
8-07 
1-23 
zom .. J 
---Vesuvius 
—-—-Iserwiese 
67-46 
59*66 
0-73 
25-94 
17-70 
5-06 
19-29 
2-38 
1-79 
Gahnite from Fahlun 
-America 
55-14 
57-09 
5-25 
2-22 
5-85 
4-55 
30-02 
34-80 
3-84 
1-22 
Chromite of Iron, 1 
13-85 
54-91 
9-69 
18-97 
0-83 
amorphous .J 
> \ 
crystallized ./ 
11-85 
60-04 
7-45 
20-13 
Franklinite.. 
0-73 
18-17 
47*52 
21-31 
10-81 
0-40 
The spinell from Aker and the pleonast from Iserwiese con¬ 
tained also a trace of protoxide of manganese. 
The formulae are as follow: 
