The Classification of Phosphates

Berzelius was first to class phosphates by their M2O-P2O5 ratio while Thomas Graham was first to classify phosphates as ortho-, pyro-, and metaphosphates in 1833. He recognized that they suffered from hydrolytic degradation or hydrolysis back to orthophosphates. For example  

It should be noted that the tripolyphosphate moiety of adenosine tripolyphosphate is the same molecule that created so much controversy about eutrophication of fresh waters. It can easily be demonstrated that solubility of phosphates in fresh water containing hardness is very low. Large bodies of fresh water can become saturated with respect to apatites in much the same way sea water is saturated. Small farm ponds are yet another consideration. Nutrients can be added to small ponds more rapidly than their concentrations can be controlled by precipitation. 

No similar reaction has ever been observed with inorganic polyphosphates except in extremely concentrated solutions at higher temperatures. In the cited case the following reaction was observed  

It is known that a solid orthophosphate passes through an amorphous phase transition when being converted to a polyphosphate. It has been emphasized in the chapter devoted to phase chemistry that a melt or a solid glassy phosphate is a solution. In the case of a dissolved salt a reaction is seldom considered to be a phase transition, because there is no change of phase. 

It was also shown that in enzyme-controlled systems 

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