Mr. M. M. Pattison Mulr on Chemical Classification, 85 



with the appearance of Black's famous research upon the mild 

 and caustic alkalies, a new era in chemical classification takes 

 its beginning. The use of quantitative experiment introduced 

 by Black was vigorously i)ursued by Cavendish, Lavoisier, 

 and the French chemists ; and soon the method began to bear 

 fruit. 



6. Lavoisier's ^Elements of Chemistry,' when compared 

 with such a work as Macquer's ' Chemistry,' published some 

 thirty years before, appears to deal with an entirely new 

 science ; or, rather, the latter book has scarcely any claim to 

 be regarded as a scientific treatise, while the former possesses 

 the requisites of such a work in a marked degree. The honour 

 which is everywhere paid to the name of Lavoisier is due to 

 him, it appears to me, not so much because of any discovery of 

 what happens when a body burns, as because of the new 

 method which he was the first to carry out systematically in 

 chemical research and in chemical classification. Lavoisier 

 endeavoured to throw aside preconceived notions concerning 

 natural objects, and to rise to true generalizations by reason- 

 ing from actually observed facts. His definition of an ele- 

 ment is still regarded as the only truly scientific definition 

 which can be adopted*. 



From a study of the products obtained by burning phos- 

 phorus, carbon, sulphur, &c. in oxygen, Lavoisier was led to 

 regard all acids as substances rich in oxygen. Further, 

 partly from his definition of an element, partly from the 

 study of the substances just mentioned, he was led to re- 

 gard every salt as formed by the union of an acid with a 

 radicle, the radicle itself, being either simple or compound. 

 This conception of the composition of salts found its full de- 

 velopment in the dualistic theory of Berzelius. 



But Lavoisier could not follow out his own method with 

 perfect exactitude. He was still so far under the trammels of 

 the school which preceded him, as to be unable to escape alto- 



* Lavoisier's words are as follows (Ker's translation of Lavoisier's 

 ' Elements of Cliemistr}^,' Preface, p. 22): — " If by the term Elements we 

 mean to express the simple and indivisible atoms of which matter is com- 

 posed, it is extremely probable we know nothing at all about them ; but 

 if we apply the term elements ov principles of bodies to express our idea of 

 the last point which analysis is capable of reaching, we must admit as 

 elements all the substances into which we are able to reduce bodies bv 

 decomposition. Not that we are entitled to affirm that those substance's 

 which we consider as simple may not themselves be compounded of two 

 or even of a greater number, of more simple principles ; but since these 

 principles cannot be separated, or, rather, since we have not hitherto dis- 

 covered the means of separating them, they act with regard to us as simple 

 substances ; and we ought never to suppose them compounded until ex- 

 periment and observation have proved them to be so."' 



