520 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



Again ammonium carbamate \loc. tit. p. 434) "when 

 heated, gives a volume of gas equal to the sum of the 

 volumes of the components of the salt." "The vapour of 

 the salt contains one-third of its volume of carbonic gas 

 and two-thirds of its volume of ammonia gas, The conden- 

 sation is consequently nil, and the density of the vapour is 



o 



the densities of the components (relatively to air) being 

 1*524 for carbonic anhydride and 0*591 for ammonia. 



The analogous case of nitric oxide, which is formed from 

 its components without condensation, had been discussed by 

 Dalton in 1802, but was explained by Avogadro (Chap. 

 XV, P- 33 8 ) on tne assumption that the molecules of 

 nitrogen and oxygen were divisible into halves, the " atom " 

 being therefore the half and not the whole molecule : 



N 2 + O 2 =-2NO. 



But if a similar method were applied to Bineau's observa- 

 tions it would be necessary to halve again the atomic weight 

 of nitrogen in ammonium chloride, ammonium cyanide, and 

 ammonium hydrosulphide, whilst in the case of the 

 carbamate it must be divided into 3 parts. This further 

 division into 2 and into 3 parts would reduce the atomic weight 



to one-sixth of Avogadro's figure, namely, = 2 '3, and the 



6 



formula of nitrogen gas would be N 12 . The carbon atom 

 would be divided into two parts in the cyanide and three 

 parts in the carbamate, thus reducing its atomic weight to 



T *2 



= 2. It would also be necessary to divide the atomic 



weight of oxygen by 3 and to reduce those of chlorine, 

 bromine, iodine and sulphur to one-half of the values 

 generally accepted for these elements. 



Such alterations were far too drastic to be justified by the 

 behaviour of a single group of substances, and therefore 



