XX 



by the oxidation of the alcohols. But what on this occasion fixed his 

 attention was the simple relation in which these acids stand to each 

 other. For the first time, indeed, we hear of the series of fatty or 

 aliphatic acids. The observations recorded by Damas have greatly 

 contributed to develop the classification of organic compounds in 

 homologous series. A very important series of this kind was indicated 

 by Dumas when, on this occasion, he showed that between formic and 

 margaric acids not less than fifteen acids could be assumed to exist, 

 differing from one another by a constant elementary difference, CH 2 , 

 of which nine at least were known at that time. 



The number of elements with which organic chemistry works in 

 building up her structures being so very limited, it was but natural 

 that from the very first considerable attention should have been 

 bestowed upon the quantitative analysis of organic substances ; and that 

 we find the very chemists who laid the foundation of organic chemistry 

 also engaged in elaborating the methods for determining the organic 

 elements. There are, indeed, no two chemists to whom we are more 

 deeply indebted for the growth of our methods of analysing organic 

 substances than Liebig and Dumas, and we are delighted that in the 

 language of the laboratory their names remain associated with the 

 processes they have introduced. We speak of Liebig's method of 

 estimating carbon and hydrogen, and of Dumas' process for deter- 

 mining nitrogen. 



Referring to the methods of determining the composition of organic 

 substances, it is but natural that we should allude to the services 

 which Dumas has rendered to organic analysis, by the revision jointly 

 carried out with Stas of the atomic weight of carbon. This revision 

 furnished the number 12 instead of 12*24, which was the number 

 adopted by Berzelius. Dumas and Stas's investigation will ever be 

 looked upon as a model for experimental researches, and their atomic 

 weight of carbon, although it has still suffered a trifling modification 

 by subsequent researches, has since been universally adopted. 



The results arrived at in this inquiry naturally also led to a revi- 

 sion of the atomic weight of oxygen in other words, to a revision of 

 the composition of water which appeared all the more desirable, 

 since chemists at that period very generally began to use the atomic 

 weight of hydrogen as the atomic unit instead of that of oxygen which 

 had been previously employed. Experiments made by Dumas on a 

 scale not hitherto attempted, and consisting in the reduction of large 

 quantities of oxide of copper from 300 to 900 grams were used and 

 determining the oxygen supplied by the oxide reduced as well as the 

 water formed, showed the volume weight of oxygen to be exactly 16, 

 and thus the fundamental numbers 1, 12, and 10 for hydrogen, carbon, 

 and oxygen were acquired which for a long time satisfied the wants 

 of chemists. 



