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LXV. Memoi7' on the L.a'w of Substitutions, and the Theory 

 of Chemical Types. By M. Dumas. 



[Continued from p. 329.] 



Chemical Types. 

 /"CONSIDERED in itself, the law of substitutions has a 

 ^-^ practical importance quite sufficient to justify the necessity 

 of distinouishing it from the more general actions of che- 

 mistry. But this distinction becomes necessary in quite 

 another way, when to this kind of instinct which led us to 

 view it at first as a law of nature, succeeds the nearly perfect 

 certainty that it is connected with one of the most mysterious 

 and most important phsenomena of the science. 



I mean the existence of chemical types, capable, without 

 being destroyed, of undergoing the most singular transforma- 

 tions, arcl of which all the elements might successively disap- 

 pear, others being substituted for them. 1 mean those organic 

 types, the admission of which into the domain of organic che- 

 mistry seemed to me to be henceforward inevitable, in con- 

 sequence of the best-characterized experiments which had 

 been suggested by the law of substitutions. 



Thus it being possible to convert acetic acid into chloracetic 

 acid by the action of ci)lorine without its at all losing its ca- 

 pacity for saturation, 1 have considered the chloracetic acid 

 which results from it as acetic acid in which chlorine had 

 been substituted for hydrogen : these two bodies have appeared 

 to me to belong to one type, to one kind. 



Now, when I established, five years ago, the analogy of 

 iodoform, of bromoform, of chloroform, and of anhydrous 

 formic acid, when I added that electro-negative bodies, such 

 as sulphur, phosphorus, and arsenic, might be substituted 

 for iodine, chlorine, and oxygen, no one raised the least dif- 

 ficulty ; this series of formula entered the science without ob- 

 stacle. 



It is then because the development of the experiment has 

 led us to look upon chlorine and hydrogen as susceptible of 

 taking the place of each other in a compound, that certain 

 convictions revolt. We are then led to examine what we 

 should understand by an organic type, and to discuss this point: 

 for example, it being possible for iodine, bromine, chlorine, 

 and oxygen to take each other's place in a compound without 

 destroying its type, can this power {I'ole) be denied to hydro- 

 gen? In other terms, iodoform, bromoform, chloroform, 

 oxiform, being admitted as species of the same genus, can 

 we refuse this character to hydroform, that is to say, to the 



