M, Dumas on the Equivalents. 213 



a + nd 



d< 



d" 



d'" 



&c. 



in which n is a whole number, either 4 or less, and d, d', d", d'" 

 the equivalents of the hydrocarbons of the series C„ H„. 

 We might have the series — 



a a + d a + 2d a + Sd a + M 



a + d' a + d + d' a + 2d + d' a + 3d+d' 



a-^2d' a + d+2d' a + 2d + 2d' 



a + 3d' a + d+Sd', 



or even 



a + d + d> + d" + d"'. 



And there are other groups in which the first member itself 

 changes, as well as the elements added to it. Tin and sethyle 

 form six different groups, which have all the characters of organic 

 radicals, and comport themselves quite like metals. If we call 

 tin a and sethyle d', we may have the formulse — 



a + d' 2a + d' 4>a + d' 

 2a + M' 4<a + 3d' 

 4a + 5d', 



in which na + nd' is the general formula, and in which a and d' 

 may be repeated to a certain extent, and d' be replaced by an 

 equivalent radical d, d", d'", &c. 



Dumas then proceeds to apply these principles to the consi- 

 deration of inorganic compounds. With reference to the group 

 fluorine, chlorine, bromine, and iodine, the equivalent of the first 

 member, fluorine, has recently been determined by Dumas by 

 converting pure fluorides of sodium and potassium into sulphates 

 of soda aud potash ; and he has obtained the number 19. The 

 numbers 19, 35-5, 80 and 127, which appear to have no arith- 

 metical relation, belong to a group similar to those seen to exist 

 among organic radicals. If we call the equivalent of fluorine a, 

 the diff"erence between that and the equivalent of chlorine d, and 

 a complementary difi'ercnce, which is required in order to pass 

 from chlorine to bromine, d', we get for fluorine, chlorine, bro- 

 mine, aud iodine, — 



a 



a-\-d 



a + 2d + d' 

 2u + 'ld + 2d'; 

 or in numbers, — 



