[ 271 3 



LIV. Extract from a Memoir on the Comlinations of PhoS' 

 pliorus with Oxygen. 



Read to the French Academy of Sciences on the \st and \BiIi 

 of July 1816. By M. Dulong*. 



JL he chief ol-ject of this paper is to ])rove that tliere are at 

 least four distinct acids, formed by the combination of phos- 

 phorus with oxvgcn. Tiie acid with the minimum of oxygen, 

 whicli I intend to call hypDphosphorous acid, is produced by the 

 reaction of water on the alkaline phosphurets. ^Vhen the latt^T 

 art' properiv prepared, there results from the decomposition which 

 they make the water undergo, phosphorated hydrogen gas in 

 variable proportions, and two acids which neutralize precisely 

 the base of the pliosphuret. One of these acids is the phosphoric 

 acid, and the other is the liypophosphorous acid. By employing 

 th.e phosphuret of barytes we may obtain very easily the latter 

 acid in its state of purity. For this purpose it is sufficient to 

 separate by the filter the insoluble phosphate from the water 

 which holds in solution the hyi)ophosphite of barytcs, and to 

 precipitate the base of this salt by an adequate quantity of sul- 

 jjlunic acid. The acid solution whicli remains may be concen- 

 tiatod by evaporation ; — pure water only is e.\tricated_, and we 

 obtain a viscous liquid strongly acid and uncrystallizable. Bva 

 stronger heat we decompose it : phosphuretted hydrogen gas 

 is ilevcloped, a little phosphorus is sublimed, and phosphoric acid 

 remains in the retort, partly combined with the glass. The 

 hypophosphorous acid acts, in general, as a very energetic de- 

 oxidant. 



Tlic liypophosphites arc remarkable by their extreme solubi- 

 lity. None are insoluliie ; those of barytes and of strontian even 

 crystallize with great diihculty; those of potash, soda, and am- 

 ntonia are soluble, in all proportions, in highly rectified alcohol. 

 That of potash is nmch n)ore deliquescent than tiie muriate of 

 lime : they absorb slowly the oxygen of the air, and become 

 acid : they are decomposed by the action of heat, giving the 

 same products with the hypophosphorous acid. 



Wf cannot effect the analysis of this acid by direct means, 

 since none of its combiuiitions can be ol)tained in the dry state. 

 In order to ascertain its proportions, 1 trr.nsfonned an indeter- 

 minate ([ua!itit'> of it into j^hospharic acid by means of chlore. 

 The quantity of chlore employed to ))roduce this effect, and the 

 weight of the phosphoric acid which results from it being known, 

 as well as tiie proportions of the latter acid, it is evident we have 

 all that is wanted to resolve the question. This analysis being 



- Annulai dt L'ltimk it de Vhjsi(juc, June 1816, p. IIJ. 



very 



