246 EEPORTS ON THE STATE OF SCIENCE. 



methyl-iodide passes into terpineol, from which, by splitting off the 

 elements of water with potassium bisulphate, dipentene is obtained. 



CH3 CH3 CH3 



c! h i 



CH, OH CHj CH HC^ CH 



II -> ! I ^ II 



CH, CH„ CH, CH, CH, CH, 



\/ ' \/ \/ 



CH . COO Et CH terpineol CH dipentene 



1 I 



C (OH) C 



CHj CH3 CH, CH3 



The products thus obtained were shown to be identical with those of 

 natural origin. 



In 1902 the examination of the distillation products of caoutchouc 

 was again taken up by Dr. C. D. Harries,^ then at Berlin, and now 

 Professor of Chemistry at Kiel. Harries assumed that the dipentene 

 was a secondary product of the decomposition of the molecules of the 

 colloid indiarubber, that the primary products were molecules of isoprene, 

 or ' di-isoprene,' and that dipentene was found from these in a secondary 

 reaction. He examined carefully the dipentene fraction of the india- 

 rubber distillate, boiling-point 150^-200°, and found that dipentene was 

 never present in greater proportion than 33 per cent., the remaining 

 portion consisting of other hydrocarbons of the formula CioH,,;. Two 

 of these were isolated. One fraction, boiling-point 147°-150° (761 mm.), 

 specitic gravity '8286 at 205, t^^ =1-4692 and molecular refraction 45'54, 

 contained no dipentene. 



He considered it to be a hydrocarbon, probably having the following 

 formula, and for which he again revived the name di-isoprene : — 



CH3 



C-CH„-CH,-CH = C-CH = CH„ 



/' ' 1 ' 



CH, CH3 



Harries regarded this as possibly identical with the hydrocarbon myrcene 

 obtained from Bay oil. 



Another fraction boiling at 168°-169° was also found to contain 

 no dipentene, no solid tetrabromide being formed. Tt does not give 

 a nitrosite, and on treatment with bromine is coloured deep violet ; 

 sp. gr. -8309 ; N„ =1-4685, mol. ref. 45-54. 



This he considered to be a new terpene, and it will be again referred 

 to later 



Emil Fischer and C. Harries - showed that when distillation of rubber 

 is carried out in a vacuum (-25 mm.) only a very small quantity of 

 isoprene or dipentene is produced, the chief products of the reaction being 

 a mixture of high-boiling hydrocarbons (boiling-point lf<0°-300°, -25 mm.). 



The action of concentrated nitric acid on the distillation products of 

 rubber was investigated by R. Ditmar.^ All the fractions boiling below 



' Jier., 35, 1902, 3260, 3266. = £er., 35, 2, 2162-2163, 1902. 



' £er., 37, 2430, 1904. 



