1867.] 



luith the Pyro- and Tetra-pliospJwric Amides. 



513 



But there is a third case in which the two atoms of hydrogen in 

 water are attacked simultaneously by two atoms of the chloride, and 

 the result is that the oxygen is left in combination with two molecules 

 of the substance originally combined with the chlorine. Here it is 

 simplest to consider that it is the water type Avhich is preserved. 



It is this third mode of action which eiplains the production of the 

 compounds containing P^... and P^.... 



If we act on oxychloride of phosphorus with water, a slow replace- 

 ment of the chlorine takes place, each atom decomposing a molecule of 

 water, and the result is — 



CI HO 

 PClO + sf; [0-3HC1 + PH00, 

 CI -^-^ HO 

 which is P H3 Op trilasic or ortlw-pliosplioric acid. If, however, we 

 employ strong solutions of potash or ammonia, the result is totally dif- 

 ferent. "We now obtain salts of an acid formed not on the type of the 

 oxychloride, but on the type of the alkaline hydrate, or water. To ex- 

 plain this the reaction must be broken up into two stages, though it is 

 not improbable that these may occur simultaneously in nature. These 

 stages are — 



2PC],0+ JJo= KCl+HCl + 5^^]=^}0, 



P Ci: r + Sl / ^'+P(H 0)! J 



which is P^ 0., pyropliosplioric acid. 



There still remains another mode of action, the replacement of 2 CI 

 in the oxychloride by 0, and tliis may be expressed in the two following 

 stages, 



PCl3 + 2^ j 0=2KCH-PC10 0, 



PCI 0+ j^|0= KC1 + P(K0)0 0, 



which is P K O3, metaplwspliate of potassium . And this is actually pro- 

 duced when the oxychloride is dropped on oxide of potassium, and a 

 similar reaction takes place with dry sesquicarbonate of ammonium. 



Eeverting to pyropliosphoric acid, if ^ ^ | be its rational 



formula, it is easy enough to understand that amides are readily formed, 

 and to see how upon neutralizing it with ammonia, one molecule of 



H is apt to be replaced by N H„ giving ^ 0)^0 ' ^ } ^' 



the pjn'ophosphamate, instead of ^ } ^' pyrophosphate 



of ammonium. 



Nor is it difficult to under.^tand the formation of pyrophosphodiamic 



