4(5 Mr. Faraday on new Compounds [Jan. 



when redistilled, began to boil at 130°, and a part remained 

 which did not rise under 200°. By repeatedly rectifying all 

 these portions, and adding similar products together, I was 

 able to diminish these dilFerences 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 be- 

 tween 176° and 190°, than at any other temperature ; large 

 quantities 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 ulti- 

 mately succeeded in separating a new compound of carbon and 

 hydrogen, which I may by anticipation distinguish as bi-car- 

 buret of hydrogen. 



Bi-carhiiret of Hydrogen. 



This substance was obtained in the first instance in the fol- 

 lowing manner : tubes containing portions of the above rec- 

 tified products were introduced into a freezing mixture at 0°; 

 many of them became turbid, probably from the presence of 

 water; one, received at 176°, (by which is meant that that was 

 the boiling point of the contents of the retort when it came 

 over) became partly solid, crystals forming round the side, 

 and a fluid remaining in the centre ; whilst two other portions, 

 one received at 186°, and the other at 190°, became quite hard. 

 A cold glass rod being introduced into one of these tubes, the 

 mass within was found to resist considerable pressure ; but by 

 breaking it down, a solid part was thrust to the bottom of the 

 tube, whilst a fluid remained above : the fluid was poured off", 

 and in this way the solid portion partly purified. The contents 

 of the tube were then allowed to fuse, and were introduced into 

 a. larger and stronger tube, furnished with another which en- 

 tered loosely within it, both being closed of course at the 

 lower end ; then again lowering the temperature of the whole 

 to 0°, bibulous paper was introduced, and pressed on to the 

 surface of the solid substance in the large tube by the end of the 

 smaller one. In this way much fluid was removed by suc- 

 cessive portions of paper, and a solid substance remained, 

 which did not become fluid until raised to 28° or 29°. To com- 

 plete the separation of the permanently fluid part, the substance 

 was allowed to melt, then cast into a cake in a tin foil mould, 

 and pressed between many folds of bibulous paper in a 

 Bramah's press, care having been taken to cool the paper, tin 

 foil, flannel, boards, and other things used, as near to 0° as 

 possible, to prevent solution of the solid substance in the fluid 

 part to be removed. It was ultimately distilled from off caustic 

 lime, to separate any water it might contain. 



