348 Analysis of Scientific Books and Memoirs. 



carbonic acid ; and from their specific gravities of these four gases, conti- 

 nental chemists have deduced their atomic weights, and have been content 

 to calculate the specific gravities of other gases consisting of oxygen, azote, 

 carbon or hydrogen. This is a deference to which we humbly apprehend 

 the experiments are not entitled. The atomic weight of hydrogen, car- 

 bon, azote, and oxygen are light compared with those of other undecom- 

 pounded substances; and we need hardly remind our chemical readers 

 that the lighter the atomic weight of an undecompounded substance is, 

 the more likely is it to be found afterwards the constituent of another 

 heavier undecompounded substance now assumed to be simple ; and con- 

 versely the heavier the atom of an undecompounded substance, the more 

 likely is it to prove compound. Thus, according to Dr Thomson, the ato- 

 mic weight of fluorine is 2.25, that of chlorine 4.5, and that of iodine 

 15.5. Iodine being the heaviest atom is most likely to be compound. So 

 far as weight is concerned, iodine viay contain chlorine, and chlorine maif 

 contain fluorine. If the question is put, may iodine be a compound of one 

 atom of fluorine (2.25) and three atoms of chlorine (4.5 X 3 = 13.5 ;) 

 we answer it by adding them together (2.25 + 13. 5) and we get the sum 

 15.75 instead of 15.5. We can therefore be certain that iodine does not 

 consist of one atom of fluorine and three atoms of chlorine ; provided al- 

 ways that we are sure the atomic weights of fluorine, chlorine, and iodine 

 are, as we have stated, 2.25, 4.5, and 13.5. The day is coming when the 

 art of analysis being exhausted in attempts to resolve into others, substan- 

 ces which resist decomposition, aid will be derived from the indirect light 

 afforded by such considerations as these. We attach, therefore, much im- 

 portance to the accurate determination of the atomic weights of such sub- 

 stances as hydrogen, carbon, azote, and oxygen ; and probably, on the 

 whole, the atomic weights of these substances may be best determined by 

 ascertaining their specific gravities. But we shall be loth to admit the 

 specific gravities of hydrogen, carbon, azote, and oxygen, as determined by 

 any experiments which are not confirmed by similar ones on carbonic oxide 

 (as well as carbonic acid,) on cyanogen, on nitrous and nitric oxides, and 

 on ammonia. If the experiments of Messrs Berzelius and Dulong had ex- 

 tended to these compounds, we would have had proofs which they them- 

 selves have not, of the accuracy of their results ; and the want of such 

 proof must ever in our eyes depreciate the value of their experiments con- 

 sidered as fundamental. 



Mr Dalton gives experiments on most of the metals, calculating gene- 

 rally from the nitric oxide evolved during their solution in nitric acid. 

 These experiments may be regarded in two points of view ; first, as they 

 afford new quantitive determinations ; second, as they add to our know- 

 ledge of chemical combinations. Viewed as quantitive determinations, we 

 can hardly regard them as of much interest. Most of the oxides he exa- 

 mines had been examined by other chemists before him, or at least have 

 been examined since his experiments were made ; and though doubtlessly 

 repetitions of quantitive experiments are of value in as far as they enable 

 us to approximate to accuracy, we cannot regard Mr Dalton's methods of 

 experimenting to be of that character which would warrant us in employ- 



