Thomson's Syxtem oj' Chemistry. 149 



simple than his, that the chance of accuracy is much increas- 

 ed. Yet as Dulong's analysis of phosphorous acid, coincides 

 almost with that of Berzelius, the subject must not be con- 

 sidered as finally settled*." Dr. Thomson's mode has more 

 pliancy, than precision, when it allows him to make the atom 

 of the same body, alternately 2.5 and 3.5, at pleasure. " There- 

 fore," adds he, " according to this view, hypophosphorous acid 

 is a compound of one atom of phosphorus, and J of an atom 

 of oxygen. Now this splitting of an atom of oxygen, not 

 merely into halves, but into^quarters, which the hypothesis of 

 Berzelius and Dulong render (renders) necessary, is, to say the 

 least of it, very unsatisfactoryf ," pauvre nfome, corps qi/on 

 vainement regarde comme indivisible ! Upon the whole, the 

 section on phosphorus is the most confused piece of writing 

 that we ever saw. 



Under sulphur in his sixth section, we again find Dr. Thom- 

 son setting up claims to discoveries, and referring to original 

 memoirs for proofs. Thus, for the composition of sulphurous 

 acid, he refers to his paper in the 6th volume of Nicholson's Sto. 

 Journal; and, on turning to it, we observe the following de- 

 termination, " Hence sulphurous acid is composed of 

 Sulphur, 68 

 Oxygen, 32 



^ foo. Page 97. 

 " The phenomena which attend the acidification of sulphur, 

 and the decomposition of sulphurous acid, render it probable 

 that sulphurous acid is rather a compound of sulphuric acid 

 and sulphur, than of sulphur and oxygen." Such are his che- 

 mical proportions and chemical philosophy in- the paper he 

 refers to. " Hence it follows," he now says, " that sulphurous 

 acid is composed of 100 sulphur -f 100 oxygen." And he 

 actually places to his own credit, and from the above paper, 

 this late determination, that sulphurous acid consists of equal 

 weights of sulphur and oxygen. The first person who demon- 

 strated this truth, was Sir M. Davy. " If the specific gravities 

 of sulphurous acid gas and oxygen be compared, and the last 

 subtracted from the first, it will appear that sulphurous acid 

 consists nearly of equal parts of oxygen and sulphur by weight. 

 In several experiments in which I burned sulphur, procured 

 from iron pyrites out of the contact of air or moisture, in dry 

 oxygen gas over mercury, I found that the volume of the 

 oxygen was very little altered| ." These are experiments in 

 which the world may confide. Dr. Thomson sinks them entirely, 

 and refers merely to his own, on which nobody can rely. 



The eighth section contains a transcript of Berzeliiis's re- 



• System, Qth edition. I, p 264. t Ibid , I., TSfi. 



J Eltmtntu qf ( htmical rhihsijthjf,^ C/S, C/1. 



