Great Exit ibition of 1 85 1 . 165 



mineral oil, containing paraffine, and occurring in a coal-mine in 

 Derbyshire. The liquid had been extensively applied by Mr 

 Young as a lubricating agent ; a use which Reichenbach had 

 long ago suggested. After a period, however, this spring ceased 

 to flow, when Mr Young applied himself to an investigation of 

 the theoretical conditions under which it might be artificially 

 formed. This gentleman saw that it would be difficult to convert 

 gas into an allotropic form, whereas it was evident that gas must 

 first come from a solid ; hence he hoped to succeed in procuring 

 the body before it assumed its gaseous state. 



The illuminating portion of coal gas consists chiefly of olefiant 

 gas, and the latter is isomeric with solid paraffine. But the allo- 

 tropism does not end here ; the peculiar slow distillation of coals 

 yielding solid paraffine, also yielded another isomeric or allotropic 

 compound, in the form of a lubricating oil, besides the additional 

 products of a burning oil, and naphtha. 



Dr Playfair now explained, by the aid of a diagram, the slow 

 distillation process of Mr Young, employed in generating his allo- 

 tropic form of olefiant gas, and directed the attention of his audience 

 to some candles made of coal paraffine on the lecture table. 



(C.} — Schrotter's process of manufacturing amorphous or allo- 

 tropic phosphorus was the third in Dr Playfair's series. The pro- 

 perties of phosphorus in its ordinary condition are well known. It 

 is spontaneously inflammable and highly poisonous ; whereas the 

 amorphous or allotropic phosphorus is neither spontaneously in- 

 flammable nor poisonous. Hence its great use in the manufacture 

 of lucifer and congreve matches ; an operation which not only im- 

 perilled the premises wherein it is conducted, but also the lives of 

 those conducting it, causing the most frightful and fatal disease of 

 the jaws and facial bones. 



Common phosphorus, when heated to about 460° or 480°, changes 

 into the allotropic condition, but a slight increment of heat changes 

 it back again. Hence the manufacture of this substance, on a large 

 scale, is attended with difficulties which Dr Playfair had no doubt 

 would be eventually overcome by the energy of Mr Sturge, the 

 patentee. The specific gravity of ordinary phosphorus is 177 — 

 of amorphous phosphorus, 1-964. Common phosphorus is soluble 

 in bisulphuret of carbon, whereas the amorphous variety is not. 

 Common phosphorus bursts into flame when brought into contact 

 with iodine, whereas the amorphous or allotropic variety does not. 

 Common phosphorus is luminous at very low temperatures, whereas 

 the amorphous variety only commences to be luminous at a tem- 

 perature of 500° Fahr. In forming lucifer matches by means of 

 allotropic phosphorus, there is experienced the difficulty that it 

 does not ignite by friction ; hence it has to be mixed either with 

 chlorate of potash, oxide of lead, or sulphuret of antimony, when 

 friction takes effect and generates flame. 



