158 On new Compounds [1825. 



was removed by successive portions of paper, and a solid sub- 

 stance 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 as possible, to prevent solution of the solid sub- 

 stance in the fluid part to be removed. It was ultimately 

 distilled from off caustic lime, to separate any water it might 

 contain. 



The general process, which appears to me to be the best for 

 the preparation of this substance only, is to distil a portion of 

 the fluid deposited during the condensation of oil-gas.,, to set 

 aside the product obtained before the temperature rises to 

 170, to collect that which comes over by 180, again separately 

 that which comes over by 190, and also the portion up to 200 

 or 210. That before 170 will upon re-distillation yield por- 

 tions to be added to those of 180 and 190; and the part 

 obtained from 190 upwards will also, when re-distilled, yield 

 quantities boiling over at 180, 190, &c. Having then these 

 three portions obtained at 180, 190, and 200, let them be 

 rectified one after the other, and the products between 175 

 and 195 received in three or four parts at successive tempera- 

 tures. Then proceed with these as before described. 



It will sometimes happen, when the proportion of bicarburet 

 of hydrogen is small in the liquid, that the rectifications must 

 be many times repeated before the fluids at 185 and 190 will 

 deposit crystals on cooling ; that is to say, before sufficient 

 of the permanently fluid part at low temperatures has been 

 removed, to leave a solution so saturated as to crystallize at 0. 



Bicarburet of hydrogen appears in common circumstances 

 as a colourless transparent liquid, having an odour resembling 

 that of oil-gas, and partaking also of that of almonds. Its 

 specific gravity is nearly 0*85 at 60. When cooled to about 

 32 it crystallizes, becoming solid ; and the portions which 

 are on the sides of the glass exhibit dendritical forms. By 

 leaving tubes containing thin solid films of it in ice-cold water, 

 and allowing the temperature to rise slowly, its fusing-point 

 was found to be very nearly 42 F. ; but when liquid, it may, 



