1 822.] Sixth Edition of his Sj/slem of Chemistry, 261 



Berzelius's canons^ which he still employs in all his reasonings^ 

 is not so general as he had supposed. This canon is as follows : 

 ** In all salts, the oxygen contained in the acid is either equal to 

 that contained in the base, or it is a multiple of it." I showed 

 in my paper that this supposed canon was inconsistent with the 

 composition of several of the phosphates. My reason for with- 

 drawing this paper was, that after it had been read I had made 

 the experiments on phosphuretted hydrogen gas (which I after- 

 wards published), and from which 1 deduced that phosphoric 

 acid is composed of 100 phosphorus + 133^ oxygen. This 

 discovery made it necessary to alter all the analytical results,, 

 because they had been calculated from incorrect data. Indeed 

 it became evident that a repetition of the analyses would be 

 necessary to ensure precision ; and to oppose Berzelius*s canon 

 with inaccurate experiments would have been both imprudent 

 and useless. 



My experiments on phosphuretted hydrogen gas were made 

 with so much care that I confided in the accuracy of my results; 

 but I was unable to reconcile them with Berzelius's analyses of 

 the phosphates ; nor was I able to prove in a satisfactory way 

 that Berzelius was wrong. 



While I was reflecting on this want of coincidence, and trying 

 to account for it, I received a short paper from Mr. Dalton, 

 which I published in the Annals of Fhilosophi/y xi. 7. He 

 informed me that he had repeated my experiments on phosphu- 

 retted hydrogen gas, and had found that it combined with twice 

 its volume of oxygen gas. The reader ought to be informed 

 that Mr. Dalton had previously made experiments on this gas, 

 and had found that it combined with its own volume, or with l4- 

 its volume of oxygen. I had every reason, therefore, to 

 confide in the accuracy of his new statement ; and I adopted it 

 the more readily, because it enabled me to reconcile Berzelius's 

 analyses with my own experiments. The sheet of the fifth edi« 

 tion of my System containing my account of phosphorus, was in 

 the press, and I altered the numbers in it so as to bring the com- 

 position of phosphoric acid to agree with the statement of 

 Dalton and the analyses of Berzelius. My own experiments I 

 applied to hypophosphorous and phosphorous acids. I repre- 

 sented the composition of the three acids as follows ; 



Phosphorus. Oxygen. 



Hypophosphorous acid ] volume + ^ volume 



Phosphorous acid 1 +1 



Phosphoric acid 1 + 1-|- 



Thus my own experiments, those of Dalton, and those of Ber- 

 zelius, all tallied with each other. The coincidence was irresis- 

 tibly seducing. I was constrained to yield to it. 



Soon after this, I went to Glasgow, and I was not in posses- 

 ion of a laboratory for nearly two years. One of the first things 



