en the Combinations of Phosphorus luith Oxygeri. 275 



any confidence. We obtain results mnch more constant by sub- 

 stituting for the pure phosplioius in the same experiment a 

 metallic phosphuret,the proportions of which may be determined 

 very exactly by synthesis, when it is prepared in the way I have 

 described. By acidifying the phosphorus by the action of the 

 chlore in contact with the water, and determining the quantity of 

 ciilore employed for this purpose, we may also attain very satis- 

 factory results. Finally, on examining by synthesis the pro- 

 portions of the chlorure of phosphorus at the maximum which 

 corresponds with the phosphoric acid, we may attain very great 

 precision. Sir H. Davy had already employed this last method. 

 Our results were so different, that I at hrst suspected there was 

 some error on my part; but having constantly obtained the same 

 numbers, I regard the following proportions as very near the 

 truth. Chlorure at the maximum : 



Phosphorus .. .. 15-4—100 



Chlore .. .. 84-6— 549-1 



100 

 Hence phosphoric acid : 



Phosphorus .. .. 44-48—100 



Oxygen .. .. 55-52— 124-8 



100 



On comparing the analysis of the phosphorous acid which we 

 have given above, with that of the phosphoric acid, we see that 

 the quantities of oxygen in these two acids arp in the ratio of 

 3 : 5, instead of 1 : 2 as Sir H. Davy has indicated. 



According to the series of the combinations of the phosphorus 

 with the oxygen, we are well founded in admitting that the 

 phosphoric acid is formed of two atoms of phosphorus and five 

 atoms of oxygen. On this supposition, and representing the 

 oxygen by 10, the relative weight of the atom of phosphorus will 

 be' 20-03 ; that of the phosphoric acid = 90-06, &c. 



1 also directed my attention, and even during a very long time, 

 to the analvsis of the phosphates, in order to discover the laws 

 of composition of those salts. M. Berzelius, from the analysis 

 of two phosf)hates onlv, has concluded that the oxygen of the 

 acid is doul)le that of the base ; but the salts which he has ex- 

 amined are certainly not neutral salts. I have analysed a great 

 number of phosphates, and I am not yet able to explain all the 

 variations which I met with in some species. 1 adhered to the 

 composition of the phosphates, in order to discover that of the 

 phosphites and hypophosphites ; the comparison of the propor- 

 tions of those different salts being very interesting in point of 



S 2 theory. 



