CUMIX. 141 



potassium and allows the cvmeiie to pass over free.* Xoad 

 obtained 7 ozs. of cymene from 1 11). of oil of cumin. Another 

 process of separating cymene is to agitate the oil of cumin with a 

 moderately concentrated solution of acid sulphite of potassium or 

 sodium, which combines with the cuminol, leaving the cymene 

 free. 



Cymene is a strongly refractive, colourless, aromatic liquid of 

 lemon-like odour, having a sp. gr. of 0-861 at 14^ C, according to 

 Gerhardt ; 0-857 at 16^ C, on the authority of Xoad ; and, accord- 

 ing to Kopp, 0-8678 at 12^ C, and 0-8778 at 0^ C. These three 

 authorities state, respectively, the boiling point to be 175°, 171^-5 

 and 177^-5 C. It is now known that pure cymene boils at 

 175*-^ C. (The earlier chemists probably operated upon impure 

 samples). 



Cymene can be obtained by mixing equal molecules of camphor 

 and phosphorous pentoxide, heating gently until the reaction 

 commences, when the flame must be removed, and pouring off the 

 cymene from the meta-phosphoric acid. It is then heated once 

 more with phosphorous pentoxide and distilled tw^o or three times 

 over sodium. It can also be obtained by distilling camphor with 

 melted chloride of zinc : a few lumps of chloride of zinc are 

 warmed in a spacious tubulated retort until they melt into a pasty 

 mass ; the camphor is then added in small portions ; the mixture 

 slightly swells up and blackens. The liquid distillate can be 

 purified from undecomposed camphor contained in it, by rectifica- 

 tion over chloride of zinc. 



Cymene can also be prepared from oil of turpentine by adding 

 4 per cent, of phosphorous trichloride and passing in one molecule 

 of chlorine for every molecule of the hydrocarbon present, the 

 temperature being kept at 25° C, and not allowed to rise above 

 that point. The product is then washed with water, dried, and 

 distilled over sodium. Thus, oil of turpentine and its isomerides 

 are converted into cymene by the loss of 2 hydrogen atoms. 



It has lung been known that cymene is obtainable from coal-tar,-|- 

 also by treating caoutchin or oil of turpentine with bromine and 

 sodium alternately,:!: and that by the action of moist carbonic acid 



* Noad, in Phil. Mag. [3] xxxii., p. 15. 



t Quarterly Journ. Chem. Soc. (1), i., p. 244. 



X Greville Williams in Phil. Mag. [4], xxxii., p. 15. 



