52 SMITHSON^IAN MISCELLANEOUS COLLECTIONS VOL. 54 



0.38044 

 0.38055 

 0.38046 



Mean, 0.38048, ± .000024 



Corrected for traces of S0„ and SO3, this becomes 0.37989. If the 

 weights of the normal litres of No and H, are 1.2507 and 0.08987, re- 

 spectively, the two gases in ammonia are combined in the ratio 1 : 3.00172. 

 Applying this datum to the densities of nitrogen and hydrogen, and 

 assuming H= 1.0078, ]Si" = 14.017, with a probable error, not exactly 

 calculable, greater than ±.0017. To combine this figure with the value 

 already found would change the latter inappreciably. Indeed, Guye and 

 Pintza regard their determinations as inferior to those made by other 

 methods, and publish their results only as a confirmation of the low 

 value for IST, as compared with the value 14.04 which had been in general 

 acceptance for many years. 



THE CARBON-OXYGEN RATIO. 



The ratio between carbon and oxygen, or in other words, the atomic 

 weight of carbon, has been directly determined by several methods. It 

 has also been indirectly computed from analyses of silver salts, such as 

 the acetate; but that group of ratios will be considered under another 

 heading. The early attempts to estimate it from analyses of hydrocar- 

 bons, have now only historic value, and can be omitted from the present 

 discussion. The direct measurements of the ratio represent three dis- 

 tinct processes : 



First, by the combustion of carbon itself. 



Second, by the combustion of carbon monoxide. 



Third, by determining the density of gaseous compounds of carbon. 



The first of these methods was used by Dumas and Stas ' in 1840, 

 and a year later by Erdmann and Marchand.^ In both investigations 

 weighed quantities of diamond, of natural graphite, and of artificial 

 graphite were burned in oxygen, and the amount of dioxide produced 

 was determined by the usual methods. The graphite employed was puri- 

 fied with extreme care by treatment with strong nitric acid and by fusion 

 with caustic alkali. I have reduced all the published weighings to a 

 common standard, so as to show in the third column the amount of 

 oxygen which combines with a unit weight (say one gramme) of carbon. 

 Taking Dumas and Stas' results first in order, we have from natural 

 graphite : 



1 Compt. Rend., 11, 991. Ann. Cliim. Phys. {.•?), 1, 1. 

 - Journ. prakt. Chem., 23, 1-59. 



