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to combust at 310 , and is completely oxidised at a red heat. 

 As a general rule, admixture of hydrogen with any of these 

 gases lowers the combustion point. Mixtures of methane and 

 carbon monoxide cannot be separated by fractional combustion, 

 but separation is possible when hydrogen, carbon monoxide, 

 and methane are all present, provided the volume of the last 

 is 50 per cent, of the mixture. 



ORGANIC CHEMISTRY. By P. Haas, D.Sc, Ph.D., St. Mary's 

 Hospital Medical School. 



In the last report reference was made to a paper by Ostro- 

 misslenski on the classification and identification of Caoutchoucs. 

 The same author has now published a series of papers (/. Russ. 

 Phys. Chem. Soc. 191 5, 47, 1885-2014) dealing with the syn- 

 thesis, structure, and vulcanisation of caoutchouc. It is found 

 that if isoprene is heated with barium peroxide and sodium at 

 60-70 it produces an abnormal caoutchouc, but if isoprene is 

 first cautiously heated alone at 80-90 it is converted into a 

 hydrocarbon containing three double bonds to which the name 

 of j3 myrcene is given. The constitution assigned to this 

 substance is represented by the formula 



CH 2 = CH - CCH 3 = CH - CH 2 - CH 2 - CCH 3 = CH 2 



If this latter compound is heated as above with barium peroxide 

 and sodium it is converted quantitatively into normal isoprene 

 caoutchouc. From these observations it is suggested that 

 plants also synthesise rubber from /3 myrcene or some similar 

 hydrocarbon rather than from isoprene, since a number of 

 substances known to occur in plants, as for example geraniol, 

 linalool, nerol, etc., should readily yield myrcene by dehydra- 

 tion. The author has also studied the question of the vulcanisa- 

 tion of rubber and has found that the process may be accelerated 

 or the temperature of vulcanisation may be lowered by carrying 

 out the reaction in the presence of an aliphatic primary or 

 secondary amine and a metallic oxide. This may be regarded 

 as a two-fold catalytic action in which the sulphur under the 

 catalytic influence of the metallic oxide combines with the 

 amine to form an unstable thiozonide according to the equation 

 2 RNH 2 -f-4S = RNH.S.S.S.NHR + H 2 S 



and this latter compound then acts as a catalyst in conveying 

 the sulphur to the caoutchouc. The fact that the corresponding 



