D. CHEMISTKY AND METALLUEGY. 215 



2.5 ; allylene, 8 ; butylene and analogues, traces ; crotonylene, 

 31 ; terene, 12; hydrocarbons, transformed into fixed poly- 

 mers, 83; diacetylene and analogous hydrocarbons, 15 (esti- 

 mated). Berthelot believes that these products arise from 

 certain fundamental reactions, already expressed in his pyro- 

 genic theory, between the four fundamental hydrocarbons 

 acetylene, ethylene, dimethyl, and methane. Together with 

 hydrogen, these bodies form a system in equilibrium such that 

 at a red heat they are all formed from any one of them pres- 

 ent at the start. If marsh gas or methane be taken, the ole- 

 fine series is directly produced from it by the abstraction of 

 hydrogen and polymerization. Acetylene produces benzene 

 (which is only triacetylene) as well as the analogous poly- 

 meric series. The more complex bodies come from the 

 more simple ones. Thus acetylene and benzene give styro- 

 lene ; acetylene and styrolene, naphthalene ; acetylene and 

 naphthalene, acenaphtene; and benzene and styrolene, anthra- 

 cene. Moreover at a dull red heat acetylene unites with 

 ethylene to form ethylacetylene, and with propylene to yield 

 propylacetylene, the former identical with crotonylene, the 

 latter with terene. In the light of this research, it is obvious 

 that the present method of determining by analysis the illu- 

 minating power of a gas, based as it is on the assumption 

 that the chief illuminants are ethylene and acetylene, is 

 worthless. Bull. Soc. Ch.^ II., xxvi., August, 1876, 104. 



rUYSICAL ISOMERISM. 



While observing the properties of a new compound discov- 

 ered by him, called nitrometachlor-nitrobenzene, Laubenhei- 

 raer has discovered the best example hitherto known of phys- 

 ical isomerism. The substance mentioned is prepared by 

 metachlor-nitrobenzene with a mixture of fuming nitric acid 

 and sulphuric acids, with the aid of heat. On pouring the 

 whole into water a yellow oil falls down, which on cooling 

 solidified almost completely to a crj^stalline mass. On in- 

 vestigation, it appears that this substance exists in four dis- 

 tinct modifications, three of which are solid and one liquid. 

 Since, chemically, there can be but one body produced in the 

 above treatment, it is obvious that the isomerism here is 

 purely physical ; a conclusion confirmed by the ready conver- 

 sion of the four forms the one into the othei'. The first, or 



