53 



CHEMISTRY. 



fire-damp has a very high kindling point; it will not inflame at the 

 red heat of wire-gauze. 



Chlorine does not act on light carburetted hydrogen, if kept in the 

 dark ; but if the light be admitted, a combination ensues, attended 

 with the formation of hydrochloric and carbonic acids. 



Olejiant gas, C^H^ ;— so called, from its property of forming an 

 oil-like liquid with chlorine. Prepared by heating a mixture of 

 strong sulphuric acid and alcohol; at first ether is formed, and 

 comes over along with vapour of alcohol ; afterwards the olefiant gas 

 comes over along with sulphurous and carbonic acid ; the two latter 

 are to be absorbed by potassa. 



Prop. — Colourless, tasteless, and inodorous ; water absorbs about 

 |th of its volume ; a non-supporter of combustion and respiration ; 

 but burns with a dense bright light, producing carbonic acid and 

 water ; mixed with a due proportion of oxygen, it explodes by means 

 of the electric spark ; sp. gr. -981 ; mixed with chlorine, it combines 

 with it in equal measures, forming a heavy, oily hquid, of sweetish 

 taste and ethereal odour. 



The gas employed for illuminating purposes is usually made from 

 coal, oil, resin, and other organic substances containing a large 

 quantity of carbon and hydrogen. The coal is distilled in cast iron 

 retorts, maintained at a bright red heat ; and the volatilized products 

 conducted through long pipes into receptacles where it is purified by 

 means of hydrate of lime. Coal gas contains a number of difl^erent 

 principles, as light carburetted hydrogen, olefiant gas, hydrogen, 

 carbonic oxide, nitrogen, and some other volatile substances. Be- 

 sides these, a number of other matters are separated in the processes 

 of condensation and purification, as tar, sulphuretted hydrogen, sul- 

 phate of ammonia, &c. The relative illuminating power of difl^erent 

 varieties of coal and oil gas depends upon the relative amount of 

 carbon and hydrogen contained ; the light being greatest when these 

 are in excess, provided always, there" be enough oxygen to burn 

 them completely. 



COMPOUNDS OF NITROGEN AND CARBON. 



Cyanogen, Bicarburet of nitrogen, NC^ or Cy. Prepared by 

 heating in a retort the bicyanide of mercury ; the cyanogen passes 

 off in the form of a gas, and the mercury sublimes. 



ProjJ. — Colourless, of a strong and peculiar odour; condenses 

 into a liquid at 45° under a pressure of 3-6 atmospheres; a non- 

 supporter of combustion, but inflammable, burning with a charac- 

 teristic purple flame, producing water and carbonic acid. Water 

 absorbs 4 or 5 times its volume, and alcohol much more ; sp. gr. 

 1-806. ^ 



Paracyanogen is the name given to the black matter left in the 

 retort after the preparation of cyanogen. 



