| abstract |
There is disclosed an improved process for preparing 1-hydroxy-3-oxa-1,2,4,5-pentane tetracarboxylic acid and 3,6-dioxa-1,2,4,5,7,8-octane hexacarboxylic acid wherein the unreacted starting acids are recovered in more desirable crystal habit. The acids are precipitated in salt form by lowering the pH of the reaction product to a range of from 4 to below 6 stepwise. The pH is lowered to above 6 in the first step and then relatively rapidly reduced to the desired level in the second step. |