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XXXIX, On the Benzole Series. — Determination of Boiling- 

 points. By Arthur H. Church, Esq* 



SINCE 1825, when Faraday discovered its first member, our 

 knowledge of the hydrocarbons of the benzole series has 

 remarkably extended : it is interesting to see from what various 

 sources these hydrocarbons have been derived ; and although 

 doubts still remain as to the relations of these bodies to one 

 another, yet their composition has been ascertained with cer- 

 tainty. Without taking notice of all these sources, it may suffice 

 to mention that the five known members of the series occur in 

 coal-naphtha, and some of them in the oil separated by the 

 addition of water to crude wood-spirit ; benzole having also 

 been obtained from oil- gas and from benzoic acid ; toluole from 

 resin-gas, balsam of Tolu, dragon's blood and toluylic acid; 

 while cumole has been procured from phorone and from cuminic 

 acid, cymole from camphor and from cumin oil. 



In experiments made for the purpose of obtaining a liquid 

 appropriate for the preservation of highly oxidizable metals, I 

 was surprised to find (oxygen being excluded) that on the appli- 

 cation of heat, sodium immersed in toluole perfectly free from 

 moisture soon became tarnished and evolved gas. This evolu- 

 tion ceased after a time, and the metallic lustre of pieces of 

 sodium placed in the liquid remained unimpaired. 



After many attempts to ascertain the origin of these phseno- 

 mena, and after having satisfied myself experimentally of the 

 absence of water from the toluole under examination, the obser- 

 vation was made that toluole, which exerted no further action on 

 sodium, tarnishes it after redistillation in the ordinary manner, 

 and it was ultimately found that the occasion of this was a pro- 

 duct of oxidation. This oxidation may be prevented, if care be 

 taken that the upper part of the retort do not reach a higher 

 temperature than that at which the liquid boils. Toluole purified 

 by sodium and distilled from a retort immersed in a bath of 

 dilute chloride of calcium solution exerts no further action on 

 sodium, and comes over to the last drop quite colourless and 

 leaving no residue. Toluole, which, in addition to the ordinary 

 methods of purification, had been treated with oil of vitriol and 

 with solution of chromic acid, behaved in the same manner. 



I was anxious to ascertain whether the boiling-point of toluole 

 was altered by the treatment with sodium. I employed in the 

 experiments several ounces of toluole from coal-naphtha, which, 

 purified in the ordinary manner, had distilled over between lOS 3 

 and 109° C. ; I also made use of toluole from toluylic acid. 

 The thermometers employed (three) were finely divided, and had 

 * Communicated by the Author. 



