148 HISTORY OF CHEMISTRY. [LECTURE VIII. 



I have intentionally chosen these particular examples. They 

 lead us to a point in Laurent's views which we have, up to 

 the present, only very superficially touched upon. Since he 

 assumed substitutions of hydrogen by nitrogen, we may inquire 

 what the equivalent of nitrogen was. We recognise, from his 

 deriving cyanogen from methylene, that Laurent assumed one 

 atom ( = 14 parts by weight) of nitrogen as equivalent to two 

 atoms or parts by weight of hydrogen. This hypothesis did not 

 accord with fact in the case of hydrobenzamide, which Laurent 

 had obtained by treating bitter almond oil with ammonia. If 

 the new substance was to be referred to the same nucleus as that 

 from which he derived benzaldehyde, then two-thirds of an atom, 

 or 9.33 parts by weight of nitrogen, must be equivalent to two 

 parts by weight of hydrogen. Laurent did not know how to get 

 out of this dilemma. The question was decided by Bineau. 50 In 

 a detailed paper the latter endeavoured, in 1838, to give a solu- 

 tion to the problem of the determination of the equivalent of 

 nitrogen. After a discussion of the fact that the common 

 method of fixing this number is very arbitrary (considering that 

 the quantity of a substance which, in its lowest stage of oxida- 

 tion, unites with ioa parts by weight of oxygen is usually 

 assumed to be equivalent to that quantity of oxygen, whereas it 

 would be quite as justifiable to start from any other stage of oxi- 

 dation), he adopts other considerations in respect to the matter. 

 He obtains his evidence chiefly from the hydrogen compounds. 

 He compares ammonia with water, and asks how many atoms 

 of oxygen are necessary in order to oxidise completely the 

 hydrogen united to one atom of nitrogen. It is known that i J 

 atoms are required for this, consequently Bineau finds 14 parts 

 by weight of nitrogen to be equivalent to 24 of oxygen and to 

 3 of hydrogen ; in other words, the equivalent of the former, 

 compared with 1 6 parts by weight of oxygen, is 9.33 = Az. He 

 introduces for nitrogen the symbol N, and points out that hydro- 

 benzamide now accords with Dumas' rule. It can very easily 

 be understood that Laurent accepted Bineau's determination. 



50 Ann. Chim. [2] 67, 225, 



