1 88 HISTORY OF CHEMISTRY. [LECTURE X. 



"equivalents" of the elementary substances (with the exception 

 of the numbers for the metals), agree almost completely with 

 the atomic weights of Berzelius, of the year 1826. It is also 

 noteworthy that Gerhardt does not mention Berzelius, and is 

 obviously quite unaware that he, to a large extent, adopts his 

 numbers. On the other hand, the Swedish chemist does not 

 appear to have noticed this agreement, since he violently attacks 

 Gerhardt's paper. 42 What I consider as most remarkable, how- 

 ever, is the fact that, at the time when Gerhardt makes his 

 proposal, very eminent chemists (I only mention Liebig and 

 his pupils 43 ) are actually employing atomic weights for the 

 most important elements, such as carbon, oxygen, hydrogen, 

 chlorine, etc., with the ratios which Gerhardt recommends as 

 new ; but that, a few years afterwards, the equivalents of Gmelin, 

 against which Gerhardt's paper was directed, are almost univer- 

 sally adopted. 



The valuable part of Gerhardt's paper consisted, however, 

 much less in the suggestion which he makes as to the " equiva- 

 lents " of the elements, than in his views respecting the equiva- 

 lents of compounds. In following up, by means of equations, 

 the decompositions of organic substances, he arrives at the 

 general proposition that the quantities of carbonic acid, water, 

 and ammonia produced in these decompositions are expressible 

 as multiples, by whole numbers, of C 2 O 4 , H 2 O 2 , and NH 3 . 44 

 Hence, according to him, these quantities must represent an 

 equal number of equivalents, whereas it was at that time as- 

 sumed that the equivalents of carbonic acid and of water were 

 only half as great as these formulae would indicate. 



Guided by quite similar considerations, he fixes the equiva- 

 lents of carbonic oxide and of sulphurous acid as G_,O 2 and 

 S 2 O 4 , and, in doing so, adds, as an important support of his 

 assumptions, that these quantities occupy exactly the same 

 space in the gaseous state. He is thus able to assert that the 



42 Berzelius, Jahresbericht 1844, 319. * Liebig (Annalen. 31, 36) 

 points out that it will probably never be possible to ascertain the true 

 atomic weights, and that it is therefore better to employ the equivalents. 

 C = 6, = 8, N=I4, H=i. 



