212 M. Dumas on the Equivalents. 



Assuming 35"5 as the equivalent of chlorine, Dumas found 

 for bromine exactly the number 80, and for iodine 127, thus 

 confirming Marignac's numbers. 



Hence the arithmetical relation may be wanting in elements 

 which belong to the same family, and exhibit the greatest 

 analogies. 



In the fourth part of his paper Dumas considers the question 

 as to whether the equivalent weights of chemical elements have 

 any relation corresponding to that which prevails among the 

 members of homologous series of organic radicals. 



The jether radicals, methyle, sethyle, propyle, butyle, &c., have 

 the equivalents — 



The difiFerence between the equivalents of two members of this 

 series is 14, and their equivalents form an arithmetical series 

 a + nd, in which the first member a is 15, and the difierence d 

 is 14. 



Many of these exhibit extraordinary relations ; and if we did 

 not know the mode of their formation, we might believe that the 

 equivalents 57 and 113, 127 and 253, &c. had the simple rela- 

 tion 1 : 2. And if we did not know whether the equivalent of 

 an element wei'e 225 or 226, the certain determination of such 

 a high equivalent would be beyond the means which chemistry 

 has at its disposal. If capryle, whose equivalent is 113, and 

 cetyle, whose equivalent is 225, do not stand in the relation 

 1 : 2, although their radicals possess the closest analogies in 

 their compounds, and obviously belong to one and the same 

 chemical family, we cannot be surprised that the equivalents of 

 molybdenum and tungsten should closely approach such a rela- 

 tion without ever actually reaching it. From these series also 

 we might form a numerous series of triads. 



But organic radicals are not always formed by the addition 

 of atomic groups ; they are also formed by substitution, as is 

 especially the case with the compound ammonias. From am- 

 monium, NH'', a large number of compound ammonias are 

 formed by the substitution of 1, 2, 3, or 4 equivalents of me- 

 thyle, tethyle, propyle, &c., for 1, 2, 3, or 4 equivalents of hy- 

 drogen. The equivalents thus produced are just as if we added 

 to ammonium, NH'', 1, 2, 3, or 4 times C„ H„. And the general 

 formula for the compound ammonia molecules, which consist of 

 ammonium a, and such hydrocarbons, would be 



