on the Atomic Theory. 115 



pound. This chemical operation is very simple, and with regard 

 to many substances, susceptible of very considerable precision. 

 Yet Richter's equivalent numbers are so erroneous, as to shew 

 that he must either have been very careless, or have employed 

 very impure salts. Wenzel, a much earlier writer, and the real 

 author of those general views which Richter prosecuted concern- 

 ing mixed saline solutions retaining the state of neutrality or 

 acidity which they previously possessed, had however made far 

 more accurate researches on the composition of salts ; but these 

 had been unaccountably neglected, though capable of furnishing 

 excellent data for the theory of chemical equivalents. 



Fischer, in the compendious table which he constructed from 

 Richter's voluminous experimental tables, states sulphuric acid at 

 1000. Hence if we divide his equivalent numbers by 20, the 

 quotients will shew their relation to sulphuric acid reckoned 50, 

 as it is on Dr. Wollaston's scale. The following are a few of 

 these quotients : 



Surely nothing but the impurity of the bodies submitted to ex- 

 periment, can account for the errors in these numbers ; the three 

 acids presenting the only tolerable approximations to truth. And 

 indeed till chemicals could be procured in a state of purity, the 

 method of research, by ascertaining the mutually precipitating 

 quantities of saline matter, was quite nugatory. At the present 

 day, however, the greater part of the most interesting saline com- 

 pounds are prepared for sale by the manufacturer, so beautifully 

 crystallized as to be quite free from impurities, and admirably 

 adapted for the investigation of equivalent numbers. Such 

 articles, made on the great scale by eminent dealers, are generally 

 to be preferred for scientific purposes to those made in little cap- 

 sules by the closet experimenter. 



When the happy idea of atomic combination was broached by 

 Mr. Dalton, chemical synthesis and analysis had become much 

 more exact, as his collation of results exhibits. In the first vo- 

 lume of his " New System/' published in 180S, we find the fol- 

 lowing numbers, reduced to oxygen 10, and sulphuric acid 50. 



The only articles here very erroneously given are azote, and its 

 compound, nitric acid. Most of the other numbers do not differ 



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