XV111 



mentioned. Here, also, the splendid papers on wood-spirit and sper- 

 maceti, jointly published by Dninas and Peligot, deserve to be 

 noticed, although they belong to a somewhat later period. 



While the experiments on the ethers sketched iu the preceding 

 paragraphs were still going on, a strange incident directed the 

 attention of Dumas to a perfectly different order of phenomena, the 

 study of which occupied him for many years of his life, and ulti- 

 mately led him to one of his finest conceptions, the theory of substi- 

 tution. It is not generally known that it is to a soiree at the Tuileries 

 that the origin of the substitution-theory must be traced. One 

 evening the visitors at the palace were greatly incommoded by irri- 

 tating vapours diffused throughout the apartments, and obviously 

 arising from the wax candles burning with a smoky flame. Alexandre 

 Brongniart, in his capacity of director of the porcelain manufactory 

 at Sevres, was looked upon as chemist to the king's household, and it 

 appeared but natural that he should be consulted respecting this 

 unpleasant incident. Brongniart intrusted his son-in-law with the 

 task of investigating the suspicious candles, and Dumas was all the 

 more inclined to engage in this inquiry, that he had already made 

 some experiments in that direction, having been asked by a merchant 

 to suggest a method of bleaching certain kinds of wax which resisted 

 the ordinary processes, and thus remained unsaleable. Nor had 

 Dumas any difficulty in supplying the explanation. The irritating 

 vapours were chlorhydric acid, and it was thus obvious that the 

 candle manufacturer supplying the palace had made use of wax 

 bleached with chlorine, and that the chlorine-bleached wax had re- . 

 tained chlorine, which during the combustion of the wax was evolved 

 in the form of chlorhydric acid. The origin of the inconvenience 

 experienced at Charles X's soiree was thus satisfactorily explained, 

 and its recurrence easily obviated. At the same time it was proved 

 by experiment that organic substances when treated with chlorine 

 are capable of fixing this element in quantities far too large to admit 

 the assumption of its presence being an accidental contamination. A 

 new field of investigation was thus opened, on which within a com- 

 paratively short time a harvest of results of startling novelty was 

 reaped by Dumas. 



It is well known that the researches suggested by the experiment 

 above mentioned led to the view of chlorine being capable of replacing 

 hydrogen, atom for atom, in organic compounds. 



This view, diametrically opposed to the dualistic conception of the 

 electrochemical theory of the time, was vehemently contested by 

 Berzelius and his school, who exhausted the resources of argument, 

 scorn, and even ridicule against them. Nevertheless, Dumas' ideas 

 rapidly took root, and but a few years later substitntional conceptions 

 began to prevail in the researches of the younger generation of 



