Help with Growth Media Precipitation

[Ron Tate]

Hello,
					I use a synthetic media to grow bacteria in order to define the 
vitamins and cofactors present.  I use charcoal treated Casein, various 
vitamins, and salts and KPO4 to buffer at pH 7.  I have made this and 
grown many many batches of bacteria with no problems until recently.  I 
am now having a problem with a precipitate forming when I adjust the pH.  
It appears to be CaPO4.  It also precitates if casein and KPO4 are the 
only ingredients present or if I adjust the pH to near 7 before I add 
the KPO4.  I have tried another source of water with the same results.  
Any suggestions will be greatly appreciated. 

Than Q
Ron Tate