Phase Relationships in Condensed Phosphates with Various Cations

Phase Relationships in Condensed Phosphates with Various Cations 

A systematic investigation of phase relationships in the field of condensed phosphates is only just beginning, though there is an extensive 

On dehydration of sodium dihydrogen monophosphate in a normal atmosphere it first passes over completely to the acid diphosphate, Na2H2P207, without forming amorphous phases. From this at temperatures above 240°C trimetaphosphate I and Maddrell s salt are formed in proportions which appear to depend in the first place on the water vapor pressure 229). Usually the low-temperature form of Maddrell s salt is the primary prod- 

Under an equilibrium pressure of water vapor the system looks much simpler. 

Applying the phase rule, it is found that, in the two component system NaP03 + H20, a maximum of four phases is possible at the quadruple points 199,302). In addition to, at the most, two crystalline substances and water vapor, an amorphous glass-like phase is always present. This phase consists of mixtures of polyphosphates, the chain length of which rises with increasing temperature. Only Na2H2P207, Maddrell s salt (h) and trimetaphosphate occur as stable solid phases in addition to NaH2P04. 

---

II. Phase Relationships in Condensed Phosphates with Various Cations.. . 9... 

---