Transactions of the Royal Society, 35 1 



to be removed. It was ultimately distilled from off caustic lime, 

 to separate any water it might contain. 



The process, which Mr. Faraday considers 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 J 80°, again separately that which 

 comes over by 190°, and also the portion up to 200° or 210°. 

 That before 170° will, upon redistillation, yield portions 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°, fyc. 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 1 95° received in three or four 

 parts at successive temperatures. Then proceed with these as 

 before described. 



Bi-carburet of hydrogen appears, under common circum- 

 stances, as a colourless transparent liquid, having an odour re- 

 sembling 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, like water and some 

 saline solutions, be cooled much below that point before any part 

 becomes solid. It contracts very much on congealing, 9 parts 

 in bulk becoming 8 very nearly ; hence its specific gravity in that 

 state is about 0.956. At 0° it appears as a white or transparent 

 substance, brittle, pulverulent, and of the hardness nearly of loaf- 

 sugar. 



It evaporates entirely when exposed to the air. Its boiling 

 point in contact with glass is 186°. The specific gravity of its 

 vapour, corrected to a temperature of 60° is nearly 40, hydrogen 

 being 1 : for 2.3 grains became 3.52 cubic inches of vapour at 

 212°. Barometer 29.98. Other experiments gave a mean ap- 

 proaching very closely to this result. 



It does not conduct electricity. 



This substance is very slightly soluble in water; very soluble 

 in fixed and volatile oils, in ether, alcohol, fyc. ; the alcoholic 

 solution being precipitated by water. It burns with a bright 

 flame and much smoke. When admitted to oxygen gas, so much 

 vapour rises as to make a powerfully detonating mixture. When 

 passed through a red-hot tube, it gradually deposits carbon, 

 yielding carburetted hydrogen gas. 



Chlorine introduced to the substance in a retort exerted but 

 little action until placed in sun-light, when dense fumes were 



2B 2 



