1818.] of Phosphorus and Oxygen. 139 



air, with an excess of oxygen, or of air, the acid which results 

 is pure phosphoric acid, without any addition of phosphorous 

 acid. Dr. Thomson adopted this method of analyzing the acid, 

 and obtained results nearly similar to those mentioned above. 

 The properties of the phosphoric acid, which forms a component 

 part of the bones of animals, appeared to possess properties 

 exactly similar, so far as regards the formation of salts, and its 

 capacity for saturation. It is necessary to observe that the 

 phosphoric acid, which is obtained by the calcination of the 

 phosphate of ammonia, is not pure, as it is impossible to remove 

 the whole of the ammonia from it. A quantity of water still 

 adheres to phosphoric acid, although it is kept for a long time in 

 a state of fusion ; and this is estimated at 20*6 parts in 100 parts 

 of the acid, which is equivalent to 18*2 parts of oxygen, almost 

 exactly the third part of the whole which is contained in phos- 

 phoric acid. 



With respect to the composition of the phosphates, M. Du- 

 long's analyses do not agree with either those of Professor 

 Berzelius, or Dr. Thomson : the salts which Berzelius examined 

 are supposed not to have been in the neutral state ; and Dr. 

 Thomson has not completed his examination of these bodies, so 

 that the subject may still be regarded as requiring further exa- 

 mination. Three points, however, seem to be ascertained; 

 1 . that the neutral phosphites are changed into phosphates with- 

 out having their neutrality destroyed ; 2. that the hypophos- 

 phites, by the same process, yield an acid phosphate ; 3. that 

 the metallic phosphurets, obtained by the process mentioned 

 above, are, in reality, merely proto-phosphurets, corresponding 

 to the protoxides which are combined with acids. With respect 

 to the weight of the atom of phosphorus, it is stated to be 20-03, 

 that of oxygen being taken as 10; as phosphoric acid is composed 

 of two atoms of phosphorus and five of oxygen, it will be repre- 

 sented by 00-06. 



It appears from the above statement respecting phosphorus, 

 that the analogy which it bears to sulphur is not so great as 

 has been generally conceived. The proportions in which phos- 

 phorus and oxygen unite are more analogous to those of azote 

 and oxygen ; and the composition of the phosphates and phos- 

 phites has also a strong analogy to those of the nitrates and 

 nitrites. On the other hand, it is to be observed that phos- 

 phorus and azote differ from each other, as much as possible, 

 with respect to their combustibility. 



