272 - Extract from a Memoir 



very complex, and resting on a great number of data deduced 

 from experiments, we cannot expect from it a perfect exactitude. 

 I found by this process, that the hypophosphorous acid was formed 

 of JOO phosphorus, and 36-3 of oxygen: but according to the 

 composition of the phosphoric acid, which may be known witli 

 the utmost })recision, the number 37'-t4, which is the three- 

 tenths of the oxygen contained in this acid, seems to be nearer 

 the truth. According to this, the hypophosphorous acid must 

 be composed of : 



Phosphorus . . 7275—100 

 Oxygen .. 27-25— 37-44. 



100 



These results are calculated upon the hypothesis that the 

 hypophosphorous acid is a binary combination ; but we may 

 entertain doubts on this method of regarding its nature, and 

 there are even strong reasons for beheving that it is a triple 

 compound of oxygen, hydrogen, and phosphorus, forming a new 

 species of hydracid. This is a question which I shall, by and 

 by, attempt to resolve. 



The acid which is immediately above the latter, results from 

 the decomposition of the chlorure of phosphorus at the mini- 

 mum, by water: it is to Sir H. Davy that we are indebted for 

 this discovery. We obtain this acid perfectly pure by evaporat- 

 ing in a proper manner the water in which the decomposition of 

 the chlorure has been effected. The whole of the muriatic acid 

 is disengaged, and, upon cooling, the acid crystallizes. It seems 

 proper to preserve to this substance the mmie of phosphorous 

 acid, which has been hitherto given to the product, from the 

 slow combustion of phosphorus, the nature of which, as we shall 

 soon see, does not agree with such a denomination. 



The true phosphites have not yet been described : their solu- 

 bility is in general much less than that of the hydrophosphites. 

 The phosphite of potash is nevertheless very deliquescent, un- 

 crystallizable, but insoluble in alcohol. Those of soda and of 

 ammonia are also very soluble in water. The former crystallizes 

 in rhomboids approaching to tlie cube. All the rest are little 

 soluble in water : those of barytes, strontian, and lime crystallize 

 by spontaneous evaporation ; but if we wish to concentrate their 

 solutions by heat, a division is made in the elements of the salt ; 

 a precipitate is formed composed of small crystals, similar to the 

 acetate of mercury: — these are salts with excess of base, abso- 

 lutely insoluliie in water. There remains in solution a salt with 

 excess of acid, which crystallizes with more difficulty. Thus 

 t]\ere exist surphosphites, subphosphites,and neutral phosphites. 



The phaenomcna presented by the calcination of the phos- 



phitefs 



