Potassium Nitrate → Tetrasodium Pyrophosphate

Participants

Reaction Steps

A stock mixture was made by mechanically blending 366 grams of STPP with 73 grams of sodium sesquicarbonate and 4.50 grams of KNO3. Two samples were taken from the mixture; one was milled in a lab pulverizing mill to approximately 100%-150 μm sieve and the other was left "as is". Both samples were calcined in a lab muffle furnace for one hour at 650° C. Assay of the samples showed that all the STPP in the milled sampled reacted with the sodium sesquicarbonate ("sesqui") to yield a calcined product with 98.9% TSPP and 1.1% metaphosphate whereas only 80% of the STPP reacted in the unmilled sample to yield a calcined product with 1.4% orthophosphate, 79.7% TSPP and 18.9% STPP. This example illustrates the importance of using a solid alkali which can be easily mixed with the solid STPP and further homogenized by milling.

Provenance & Evidence