LECTURE VII.] HISTORY OF CHEMISTRY. 113 



another. Nevertheless Berzelius himself afterwards assisted 

 more than anyone else in extending the laws of stochiometry 

 to organic chemistry, inasmuch as he materially improved the 

 method of elementary analysis employed at that time, and 

 thereby provided himself and others with the means of ascer- 

 taining the composition of organic substances. 



It may not be out of place to give some account here of 

 the history of elementary analysis, just because the views 

 respecting organic compounds were essentially changed in 

 consequence of its development. 



I shall not again revert to Lavoisier's method, which I have 

 already indicated in an earlier lecture. 6 There are almost 

 thirty years between his experiments and those of his nearest 

 successors. I pass over the experiments of Saussure, 7 Ber- 

 thollet, 8 etc., as well as the first labours of Berzelius 9 upon 

 this subject. These furnished analytical processes that were 

 sufficient, perhaps, in special cases, but cannot by any means 

 be regarded as general methods. On the other hand, the 

 investigation of Gay-Lussac and Thenard, in 1811, deserves 

 our attention. 10 They burned the organic substance with 

 potassium chlorate, by forming small pellets of the mixture and 

 allowing these to fall into a perpendicularly placed tube, the 

 lower end of which was heated red-hot. The tube was closed 

 above by means of a stop-cock furnished with a recess designed 

 for the reception of the pellets. The gases from the combustion 

 had to make their escape through a side tube into a eudiometer, 

 and they were there measured. Gay-Lussac and Thenard then 

 absorbed the carbonic anhydride formed, and determined the 

 oxygen left behind. They knew, further, the quantity of sub- 

 stance burned and the quantity of potassium chlorate mixed 

 with it. By the help of Lavoisier's equation : 

 Substance + Oxygen employed = Carbonic anhydride + Water 



6 See pp. 28-29. 7 Journ. de Phys. 64, 316 ; Bibliotheque britannique. 

 54, No. 4 ; 56, 344 ; Ann. Phil. 4, 34. 8 Mem. d'Arcueil. 3, 64 : 

 Mem. de 1'Acad. 1810, 121. 9 Gilb. Ann. 40 (1812), 246. 10 Rech. phys. 

 chim. 2, 265. 



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