ERRORS OF WEIGHING. 



39 



expressed by one single number, this analytical ratio, a, 

 which is the amount of product obtained for the unit of 

 weight of substance. 



This ratio is, as stated above in words : a = -H- . 



In order that there may be no misunderstanding about 

 this most important though really very simple matter, 

 we will take from the record one of the most noted cases, 

 namely the five combustions of diamond in oxygen by 

 Dumas in 1840. 



We copy the data from the original publication, Annales 

 de Chimie et de Physique, 3rd series, Tome I, for January, 

 1841. It is reprinted in the " Oeuvres" of Stas, vol. I, pp. 

 235-287 ; Brussels, 1894. See also our True Atomic Weights, 

 pp. 20-22, 1894. 



Dumas. Combustion of the Diamond. 



This is all we learn from the five famous combustions of 

 diamond made by Dumas in 1840, and in which Stas was 

 privileged to assist. 



The five combustions are each represented by the final 

 analytical ratios (product obtained divided by substance 

 used). 



These ratios represent the weight of carbon dioxide 

 obtained by the combustion of a unit of weight of the pure 

 carbon of the diamond. 



These five ratios agree so closely that we are authorized 

 to calculate the mean value of all. 



But we must not conclude that this mean value 3.66 63 

 more nearly represents the true value than either one of 

 these individual ratios. 



