1883.] Molecular Weights of the Substituted Ammonias. 349 



and lower molecular weights being revealed by the analysis. ~No 

 doubt, the amount of this impurity is exceedingly small, but still 

 sufficient to prevent a definite conclusion being reached as to the 

 correct value for pure triethylamine. As Stas's method of titration 

 is capable of giving concordant results within one ten-thousandth 

 of the molecular weight, the large variation, amounting to one four 

 hundred and fortieth of the mean molecular weight of the first and 

 third sample of the last fractionation, shows that the material is by no 

 means pure enough for the problem we desire to solve. At the same 

 time, the middle and largest portion of the last distillation has probably 

 a molecular weight very near that of the pure base, and may provi- 

 sionally be accepted. If the molecular weight of the hydrobromate is 

 182*012, then the value for triethylammonium is 102*061 ; and if we 

 subtract from this the value for ammonium found by a similar method 

 of titration, viz., 18*074 (Stas), the resulting number 83*987 is the 

 molecular weight of the hydrocarbon molecule C 6 H 12 . This value is 

 probably as accurate a value of the molecular weight of a hydrocarbon 

 as has been hitherto determined, and is sufficient to prove that if 

 hydrogen has the atomic weight of unity, then carbon is twelve, 

 and thus the addition of six atoms of carbon to twelve atoms of 

 hydrogen results in a compound the molecular weight of which 

 may be expressed as a whole number, viz., 84, within the limits 

 of experimental error. This value may be due to the summa- 

 tion of positive and negative variations from the respective values 

 of 1 and 12 for hydrogen and carbon required by Prout's law, 

 and therefore in itself would not prove anything about the law 

 of whole numbers in either atom, unless other methods enabled the 

 atomic weight of carbon or hydrogen to be otherwise defined. 

 Now the labours of Dumas and Stas have shown that if oxygen is 

 taken as 16, then carbon is 12*005, so that the number 83*987 for 

 C 6 H 12 would necessitate hydrogen being rather less than 1 instead 

 of being more, as generally acknowledged when = 16 is taken 

 as the standard. Whatever conclusions further investigation may 

 induce chemists to adopt, there can be no doubt the present method 

 is capable of very great refinement in the determination of the 

 molecular weights of hydrocarbon radicals, and when exhaustively 

 treated must lead to results of importance. We intend to continue 

 this investigation, employing other bases than triethylamine, and 

 trust to reach more definite conclusions by working on material of 

 greater purity. We will leave for future discussion Schiitzenberger's 

 investigation on the variability of the atomic weight of carbon, which 

 is very far from being confirmed by the method of verification we have 

 adopted. 



