Sodium Dihydrogen Phosphate (SDP) is an inorganic compound of sodium and dihydrogen phosphate ions. It is produced by partial neutralization of phosphoric acid. It occurs in anhydrous as well as mono and di hydrate. It is a white powder or colorless crystal soluble in water and slightly soluble in alcohol. Sodium phosphates are inexpensive and non-toxic.
The method of making mono-sodium phosphate which consists in reacting upon dicalcium phosphate with sodium bin-oxalate and then removing the calcium oxalate formed from the resulting solution of monosodium phosphate, then reacting upon the calcium oxalate with boiling sodium carbonate to produce sodium oxalate. and then adding the required amount of an acid to produce sodium binoxalate for re-introduction into the process.
SDP is used as an emulsifier in foods along with di/tri- sodium phosphate, dipotassium phosphate etc. It acts as a buffer and helps regulate pH of cheese and other foodstuffs. It quickens gelation in custard pudding and other baked foods. It is used to bring tartness to non-cola beverages because of its acidifying effects. It also helps in retaining the color of eggs. Other uses include sequestrant, quality enhancer and leavening agent.
It is further used in boiler water treatment, baking powder manufacturing, acid cleaning, cattle feed supplement, electroplating, as a laboratory reagent and a phosphate source in Effluent treatment.