Mr. Faraday 
120° 
on 
7iew compounds 
13.2 
2.9 
130° 
- 
- 
16.1 
- 
3.2 
140® 
- 
- 
19.3 
- 
- 
3.1 
150° 
- 
- 
22.4 
- 
- 
3.2 
160° 
- 
- 
25.6 
- 
- 
3.4 
170® 
- 
- 
29.0 
- 
- 
15.7 
180° 
- 
- 
44.7 
- 
- 
23.4 
190® 
- 
- 
68.1 
- 
- 
23.4 
200° 
- 
- 
84.2 
- 
- 
16.1 
210® 
- 
- 
- 
- 
7.4 
220° 
- 
- 
95-3 
- 
- 
3.7 
230 ° 
- 
- 
96.6 
- 
- 
1.3 
The residue 3.4 parts was dissipated before 250® with slight 
decomposition. The third column expresses the quantity 
volatilized between each 10°, and indicates the existence of 
what has been described as bi-carburet of hydrogen in con- 
siderable quantity. 
The importance of these vapours in oil gas, as contributing to 
its very high illuminating powers, will be appreciated, when it 
is considered that with many of them, and those of the denser 
kind, it is quite saturated. On distilling a portion of liquid, 
which had condensed in the pipes leading to an oil gas gas- 
ometer, and given to me by Mr. Hennel, of the Apothecaries’ 
Hall, I found it to contain portions of the bi-carburet of 
hydrogen. It was detected by submitting the small quantity 
of liquid which distilled over before 190° to a cold of 0°, when 
the substance crystallized from the solution. It is evident 
therefore, that the gas from which it was deposited must 
have been saturated with it. On distilling a portion of recent 
