443 
of carbon and hydrogen^ &c. 
The heat continued gradually to rise, and before the substance 
was all volatized, it had attained 250°. 
With the hope of separating some distinct substances from 
this evident mixture, a quantity of it was distilled, and the 
vapours condensed at a temperature of 0° into separate por- 
tions, the receiver being changed with each rise of 10° in the 
retort, and the liquid retained in a state of incipient ebullition. 
In this way a succession of products were obtained ; but they 
were by no means constant ; for the portions, for instance, 
which came over when the fluid was boiling from 160® to 
170°, when redistilled, began to boil at 130°, and a part re- 
mained which did not rise under 200°. By repeatedly recti- 
fying all these portions, and adding similar products toge- 
ther, I was able to diminish these differences of temperature, 
and at last bring them more nearly to resemble a series of 
substances of different volatility. During these operations I 
had occasion to remark, that the boiling point was more 
constant at, or between 176° and 190°, than at any other 
temperature ; large quantiti^ of fluid distilling over without 
any change in the degree ; whilst in other parts of the series 
it was constantly rising. This induced me to search in the 
products obtained between these points for some definite 
substance, and I ultimately succeeded in separating a new 
compound of carbon and hydrogen, which I may by anticipa- 
tion distinguish as bi-carburet of hydrogen. 
Bi-carhuret of hydrogen. 
This substance was obtained in the first instance in the 
following manner : tubes containing portions of the above 
rectified products were introduced into a freezing mixture at 
MDCCCXXV. 3 M 
