Traite Elementaire des Reactifs. 327 



article. Its authors liave been for some time active contributors to 

 the Journal de Pharmacie. M. Payen, who is a manufacturer of 

 sal ammoniac, lately wrote a good memoir on the discolouring 

 properties of charcoal, to which the second prize was awarded by 

 the Pharmaceutical Society of Paris. M. Chevallier published 

 some time since an Analysis of the Mineral Waters of Pontivy ; 

 and the two gentlemen conjoined, inserted in the Journal de Phar- 

 macie for September last, Experiments on the colouring matter of 

 the Petals of the Malva Silvestris, and of the wood of St. Lucie 

 (Cerasus Malahcb) employed as reagents, in which they sought to 

 appreciate numerically their sensibility to alkalis and acids, com- 

 pared with other coloured tests. 



We were accordingly willing to expect, in a new- treatise on 

 chemical tests, published in the French capital, some novelty in the 

 agents, or some ingenuity in their applications ; something, in fact, 

 to justify the appearance of such a work soon after the third edition 

 of Thenard. But we are sorry to acknowledge that our expecta- 

 tions have been greatly disappointed. 



MM. Payen and Chevallier have not, in reality, indicated any 

 method of re-agency which is not better described in the Professor's 

 treatise; while they seem to be unacquainted with many things 

 which had been long ago effected in the same department by Berg- 

 man, whose treatise on the analysis of mineral waters, as far as 

 his plan required, presents more minute and delicate rules of testing 

 than we can find in the recent Traite. 



The work is inscribed, in terms of merited respect, to M. Vau- 

 quclin, under whose superintendence they profess to have made 

 their chemical studies. We wish they had consulted some of his 

 excellent formulae of analysis, from which they might have gleaned 

 many ingenious tests. 



In a short introduction they give a definition and description of 

 the term re-agent, to which they subjoin the plan of the subsequent 

 book. " Re-agents," they say, " are bodies which, placed in 

 contact with others, give rise to new combinaticns ; and which, 

 during their re-action, produce peculiar and characteristic pheno- 

 mena, which serve to make these bodies be recognised." Many 

 things, however, which it would be difficult to bring under the 

 above definition, are certainly re-agents ; such as change of tem- 

 perature, (or heat,) electricity, and magnetism. We would, there- 

 fore, say, that a chemical re-agent or test is a known body or 

 power, which, being applied to an unknown substance, serves to 

 point out, by characteristic phenomena, its nature or constituents. 



Their work is divided into nine chapters. In the first they treat 

 of the forms of bodies, of specific gravity, of the influence of bodies 

 foreign to the combination, of the action of light and electricity. 

 The second chapter discusses caloric, its ac(^ion on different bodies, 

 and the phenomena to which it gives rise. The third treats of the 

 employment of simple combustible bodies non-metallic and mc- 



