Mr Daltoxi's System of Chemical Philosophy. 353 



ture as hair is in common mortar. In like manner small quanti- 

 ties of other metals or alloys are often added, for the purpose, as it strikes 

 us, of imparting mechanical properties, by mixture rather than by combi- 

 nation. But besides combined and mixed alloys, we should regard it 

 quite possible, that some alloys in the solid state, are in fact frozen solu- 

 iions. Mercury, there is no doubt, is capable of holding some amal- 

 gams in solution ; and till experiment shall contradict the supposition, we 

 shall regard it as conceivable and probable, that some melted masses of 

 metal will prove to be solutions of one metal or alloy in another metal or 

 alloy ; and that the solid masses derived from such liquids are congealed 

 solutions. 



In their present state of ignorance, chemists will regard Mr Dalton's 

 contributions to our knowledge of alloys as an acquisition. But it appears 

 to us, that Mr Dalton has been too scantily furnished with information 

 by practical persons, to render his views available in the arts. 



Under the last section, Mr Dalton gives some useful experiments on the 

 triple allojjs of lead, tin, and bismuth. 



The appendix contains a number of remarks which will interest the stu- 

 dious chemist. We were very well pleased with the following judicious 

 strictures on a table of the specific heat of thirteen metals published by 

 Messrs Dulong and Petit. We need not quote this table ; because it has 

 already obtained a place in almost every elementary chemical book ; and 

 we need hardly remind the reader that they profess to have discovered that 

 the atomic weight of a substance multiplied by its specific heat should give 

 a constant product. 



" The Essay of MM. Dulong and Petit, in the tenth volume of the .4fi. 

 de Chimie (see An. of Philosophy, vol. 14th, 1819) manifests great inge- 

 nuity. It does not appear, however, so fortunate either in theory or expe- 

 riment as the former one. It would be diflicult to convince any one, either 

 by reasoning or by experience, that a number of particles of mercury at the 

 temperature of — 40°, whether in the solid, liquid, or elastic state, have all 

 the same capacity for heat. Indeed the experiments of De la Roche and 

 Berard, if they are to be credited, demonstrate the inferior capacity of con- 

 densed air to rarefied air ; and if the same body changes its capacity in the 

 elastic form, it may well be concluded that all the three forms have not the 

 same capacity. MM. Dulong and Petit have themselves shown, in their 

 former essay, (see page 276) that solid bodies vary in their capacities for 

 heat, and that scarcely any two bodies vary alike ; hence it is impossible that 

 the product of the weight of the atom and specific heat of the body should be 

 a constant quantity. Their specific heat of certain metals differ greatly 

 from what is found by others. For instance, they make the specific heat 

 of lead .0293 ; the lowest authority I have seen is Crawford, .0352, and the 

 highest Kirwan .050 ; from repeated trials I have lately found it, upon an 

 average, .032. The weights of some of the atoms in their table differ ma- 

 terially from what are commonly received ; for instance, bismuth is 13.3 

 instead of 9 ; also copper, silver, and cobalt, are only half the weights of 

 some authors. The gases too arc unfortunate examples. Oxygen gas gives 

 a product of .236 instead of .375 ; azotic gas gives a product .1967, if oxy- 



