350 Analysis of Scientific Books. 



condensed at a temperature of 0° into separate portions, 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 re-distilled, 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, our author 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 he remarked, that the boiling point was more 

 constant at, or between 176° and 190°, than at any other tempera- 

 ture ; large quantities of fluid distilling over without any change 

 in the degree ; whilst in other parts of the series it was con- 

 stantly rising. This induced him to search in the products ob- 

 tained between these points for some definite substance, and he 

 ultimately succeeded in separating a new compound of carbon and 

 hydrogen, which he calls bi-carburet of hydrogen. 



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

 lowing manner : tubes containing portions of the above rectified 

 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 remain- 

 ing 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 re- 

 mained 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, were introduced into a larger and stronger tube, 

 furnished with another which entered 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. Jn this way much fluid was 

 removed by successive portions of paper, and a solid substance 

 remained, which did not become fluid until raised to 28° or 29°. 

 To complete 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 pos- 

 sible, to prevent solution of the solid substance in the fluid part 



