( S. A. P. P ( Sodium Acid Pyrophosphate

S. A. P. P. (Sodium Acid Pyrophosphate)
S. A. P. P. is  Sodium Acid Pyrophosphate (Na2H2P2 O7) . 
S. A. P. P. is used to “treat out” soluble Calcium form Gyp or cement contamination. It is still effective at temperatures above 82 oC  (180oF).
S. A. P. P. may also be used as a thinner in low pH muds where temperatures do not exceed 82 oC  (180oF).