HYPOPHOSPHOROUS ACID. 343 



of phosphorus covered by the liquid chloride of phosphorus 

 (P C1 3 ), in an open bolt-head. Phosphoric acid is formed, and 

 also a yellow matter, which he finds to be a phosphate of the 

 oxide of phosphorus, and which gives a yellow solution with 

 water. This solution is decomposed about 176, and a floccu- 

 lent yellow matter subsides, which is a hydrate of the oxide of 

 phosphorus, nearly insoluble in water. This compound aban- 

 dons its combined water, when dried in vacuo over sulphuric 

 acid, or when cooled below 32, when the water separates as 

 ice, and oxide of phosphorus remains perfectly pure. 



The oxide of phosphorus is a powder of a canary yellow co- 

 lour, denser than water, and soluble neither in water, alcohol, 

 nor ether. It may be kept in dry air without change. It re- 

 sists a temperature of 570 without decomposition, but assumes 

 a lively red colour ; and does not take fire in air till heated a 

 little above the boiling point of mercury. This oxide absorbs 

 dry ammoniacal gas, and appears to form feeble combinations 

 with the fixed alkalies. Leverrier assigns to its hydrate the 

 composition P 2 O n '-2HO, and to its phosphate, 2P 2 O + 3PO & . 



HYPOPHO3PHOROUS ACID. 

 Eg. 492.28 or 3D.44 ; PO 5 not isolable. 



This acid was discovered in I81G by Dulong.* It was ob- 

 tained by the action of water upon the phosphuret of barium, 

 of which the phosphorus of one portion oxidates and becomes 

 the acid in question, at the expense of the water, while the 

 phosphorus of another portion, combining with the hydrogen 

 of the water, produces phosphuretted hydrogen gas. Rose pre- 

 pares the same hypophosphite of barytes, by boiling phospho- 

 rus and caustic barytes together, till all the phosphorus disap- 

 pears and the vapours have no longer the smell of garlic.f 

 This solution is filtered, and to separate the hyphosphorous 

 acid from barytes, diluted sulphuric acid is added which 

 precipitates the latter. The acid remaining in solution may be 

 concentrated with caution, to the consistence of a thick syrup, 

 but affords no crystals. More strongly heated, this hydrate of 



* An. cle Ch. et de Ph. t. 2. p. 141. 



f II. Rose, sur les Hypophosphites, An. tie Ch. et de Hi. t. 38, p. 258. 



