2 66 
Analysis of Dolomite. 
[Sept. 
As the atomic weight of magnesia and lime differ considerably, the quantity of 
carbonic acid extricated in their calcination, provided there be no third substance 
present, is a sufficient datum whence to calculate the proportions of the two earths 
in a compound ; but the process requires great accuracy of manipulation, as every 
error will be magnified tenfold in the result ; and it also depends upon the correct- 
ness of the equivalent numbers of magnesia and lime, which are given variously by 
different authorities ; — having found those of Berzelius most consistent with my 
own experiments upon crystallized dolomite, I have adopted his determinations, 
which are as follows : 
Lime, - 
Carbonic acid, 
Magnesia, 
Water, 
28.47 1 
22.15 / 
20.70 j 
9.01/ 
50.62 
12.85 
In any compound then of the two, calling the carbonate of lime l, and that of 
magnesia m, and the acid in each c and c' ; also making C the weight of gas lost 
by calcination on 1U0 grains, we shall have 
/ •j- m — 100 c -4- e C 
c — 0.4376 / and c — 0.5169 ?n 
0 
Therefore, 1.1813 »n =^— ^ — l 
and deducting 
we obtain 
0.4376 
m = 100 — l 
0.1813 m = 2.285 C — 100 
2.285 C — 100 
0.1813 
/ = 100 — m 
I have made use of this formula in the second column of the accompanying table, 
excepting in the case of dolomite, which being supposed a priori to be a definite 
47.2 
compound, should have its acid divided equally between the two earths : — Tlius ■ ■— - 
or 23.6 Carb. A is equivalent to Carb. Lime, 54. 0 1 QQ , 
and Carb. Mag. 45. 7 J ’ ' 
which differs so little from 100, that the error may be safely attributed to the pro- 
cess or the tables. The formula above would only give 43,4 magnesia. The error 
would disappear, were the loss of carbonic acid 0.2 gr. more, which was the case in 
former experiments. 
The magnesia which I employed was taken from a medicine chest and dried, but 
it seems to contain 10§ per cent, of water existing hygroinetrically, as I ascertained 
by direct experiment. It is necessary therefore to modify the value of c' in the 
formula, which becomes m = 2.285 c — 100 -4-0.311. 
I shall now proceed to the experiments. 
TABLE I. 
Loss of 
Calculated 
Carb . 
No. 
Composition • 
Curb. A. 
Water 
Lime 
by heat. 
C.L. 
C. M. 
absorbed. 
deduced. 
1:1 
Rhombohedral calcareous J 
spar. 
43.9 
43.8 
100 
0 
18.06 
18.00 
100 
3 . ) 
The same with 20 per cent. J 
4664 
79 
21 
15.04 
83 
4 . r 
magnesia. ( 
46.70 
16.00 
89 
H 
The same with 45 per cent. J 
49.70 
56 
44 
10.4 
57.5 
6.f 
magnesia. ) 
7. 
Ditto, 80 per cent, magnesia. 
54.44 
22 
78 
5.9 
32.5 
8. 
Carb. mag. (another day) 
57. 5 
0 
100 
0 . 
0 
9. 
10. 
Nerbudda crys. t 
Dolomite. ( 
47.20 
47.20 
54.2 
45.8 
10.4 
57.5 
11. 
12. 
Do. with 20 per cent, of j 
rhomb, spar. | 
46.56 
46 56 
64.6 
35.4 
12.8 
72 
13 
Polyhedral gr. dolomite. 
46.16 
69.8 
30.2 
10.1 
56 
14. 
Do. with 80 per ct. lime. 
44.22 
94 
6.0 
16.3 
92 
15. 
White marble. 
44.08 
100.7 
0 
18.4 
102.5 
