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CHEMICAL SCIENCE. 



ON GERHARDT'S DISCOVERY OF ANHYDROUS ORGANIC ACIDS. 



The following paper was recently read before the Royal Institution, 

 England, by Prof. Williamson. The discovery by M. Gerhardt, of a 

 number of anhydrous organic acids has thrown so much light on one 

 of the most important questions of chemical philosophy, that it con- 

 stitutes one of the most remarkable illustrations of the manner in which 

 the rich materials of organic chemistry may be brought to bear on 

 the explanation of the phenomena of chemical action, and the laws of 

 chemical combination. It is not unworthy of remark, that the bodies 

 prepared by Gerhardt, had for some years past been supposed to exist 

 ready formed in combination with water and other bases, and that the 

 chief objection to that supposition was founded on the circumstance of 

 their never having been separated from such combination, and pre- 

 sented in an isolated form. In fact, Gerhardt has supplied the very 

 link in the chain, which was expected to constitute evidence for a 

 familiar theory of the constitution of salts. But the process by which 

 the result was attained, is even more important than the result itself, 

 and has led to our drawing from that result a conclusion different from 

 that which was generally expected. Chemistry aims at discovering 

 the nature of that action by which substances of opposite properties 

 undergo those remarkable changes which we call chemical combina- 

 tion ; and it naturally follows from this view of its objects, that chemi- 

 cal science is more advanced by the discovery of a new process, than 

 by the discovery of a new substance ; and its theories are more im- 

 mediately affected by the nature of a process of change, than by any 

 physical fact, such as the existence of a peculiar body or class of bodies. 

 Thus it is that the method of isolating the anhydrous organic acids, 

 has afforded evidence of a new view of the constitution of acids and 

 salts. A few words may serve to give an idea of the previous state of 

 the question. Compounds of oxygen-acids were supposed to consist 

 of the anhydrous acid united with an oxide. Thus hydrated sulphuric 

 acid was represented as containing the anhydrous group S O 3 plus an 

 atom of water H 2 O ; and in the saturation of this hydrated acid by a 

 base such as potash, it was conceived that this oxide replaced the wa- 



