IQO HISTORY OF CHEMISTRY. [LECTURE X. 



the base in a salt, or, as it can also be expressed, that the 

 usually hypothetical anhydrides (instead of the hydrates) were 

 regarded as acids. Thus, on the basis of the atomic weights of 

 Berzelius, the analysis of acetate of potash led to the formula 

 K.C 4 H 6 O 4 , and from this, after deduction of the potash, KO, 

 the atom of acetic acid remained as C 4 H 6 O 3 , which did not 

 permit of any further division. Those who regarded atom and 

 equivalent as identical had to find confirmation of the accuracy 

 of this formula in the fact that this quantity of acetic acid is 

 neutralised by one equivalent of potash, KO ; and so the 

 formulae of all monobasic acids were necessarily doubled. 

 The establishment of the theory of polybasic acids caused 

 Liebig to double the formulae of several dibasic acids, as for 

 example, that of tartaric acid (see p. 159). This, in turn, affected 

 the atomic magnitudes of neutral substances, such as alcohol, 

 compound ethers, etc. To the first of these the formula 

 C 2 H 6 O, corresponding to two volumes, had at first been as- 

 signed, and, in order to arrive at this formula, Berzelius 

 assumed a radical in alcohol different from that in ether. 45 But 

 Liebig, with whom alcohol was the hydrate of ether, adopted 

 the group ethyl, C 4 H 10 , as the basis of both, 46 and the close 

 relations between alcohol and acetic acid then became promi- 

 nent for the first time. Ethylene was now written C 4 H f , and 

 chloride of ethyl C 4 H 10 C1 2 ; that is to say, all the compounds of 

 the ethyl series contained four atoms of carbon. Quite similar 

 reasons caused the doubling of the other formulae. 



Gerhardt wishes, as we have stated, to halve these, and he 

 is moved to do so from other points of view besides that of the 

 volume relations. According to him, the salt-forming metallic 

 oxides do not consist, as Berzelius assumes, of one atom of 

 metal and one of oxygen, but they are comparable with water 

 (which he now writes H 2 O) and contain two atoms of metal ; 4 ~ 

 whereas in the hydroxides one atom of metal and one of 

 hydrogen are united with one atom of oxygen. 48 He is there- 



45 Compare p. 132. ^ Compare p. 133. 4 " Compare also Griffin, 

 Chemical Recreations, Seventh Edition (1834), 92-93 and 228-229, 

 48 Ann, Chim. [3] 18, 266. 



