CHARLES ADOLPHE WURTZ. 569 



Subsequently he studied the action of sodium on the iodides of the 

 alcohol n.di:als. Previously, by the action of zinc on the iodide of 

 ethyl and methyl, Frankland had succeeded in isolating hydro-carbon, 

 which he regarded as the actual alcohol radical; but Wurtz, using a 

 mixture of the iodide of two radicals, found that he obtained a homo- 

 geneous product, which was formed by a union of the two radicals. 

 This left no doubt that Frankland's radical substance was also formed 

 by the union of two molecules of methyl or ethyl, and rendered our 

 views of the relations of such radicals much clearer than before. In 

 order to define the radicals of organic chemistry more accurately, 

 Wurtz introduced the term " rest," and enunciated the rule, which for 

 a long time held an important place in the science, "that the atomicity 

 of a compound radical is always equal to the number of hydrogen 

 atoms, or their equivalents, which the rest may be regarded as having 

 lost." 



Soon after followed Wurtz's remarkable investigations on the 

 glycols, and oxide of ethylene, by which he not only defined the di- 

 atomic alcohols, and gave us our first accurate knowledge of these 

 bodies, but also developed the theory of types into the larger doctrine 

 of quantivalence, in which he recognized the determining cause of 

 molcular structure ; and it was in the discussion on the constitution of 

 lactic acid which followed this investigation that Wurtz made the dis- 

 tinction between basicity and atomicity. Subsequently, by the action 

 of hydriodic acid on araylene, Wurtz obtained a product isomeric with 

 amyl alcohol, and the investigation of this new substance resulted in 

 defining the relations of the now well-known class of tertiary alcohols. 

 We must not forget to mention also the synthesis of the oxygen 

 bases, including that of choline, — so interesting as one of the proxi- 

 mate principles of the animal economy ; also the synthesis of the 

 aromatic acids, followed during these last years by a study of the con- 

 densation products from aldehyde, by which he isolated aldol and other 

 compounds after the same type. 



Among Wurtz's later investigations is one into which he was led 

 by a controversy with some of his colleagues iu the French Academy, 

 in regard to abnormal vapor densities as bearing on the validity of 

 the law of Avoijadro. The discussion chiefiv turned on the action 

 of heat on hydrate of chloral, and by a most ingenious series of 

 experiments Wurtz proved that aqueous vapor was present as such 

 in the vapor of this substance, and therefore that the apparent ab- 

 normal vapor density of hydrate of chloral was due to disassociation. 



This controversy indicated Wurtz's nearly isolated position among 



