Sodium hypophosphite has two chemical formulas: NaH2PO2.H2Oand NaH2PO2. One contains one molecule of water of crystallization, while the other is anhydrous. The CAS numbers for the monohydrate and anhydrous forms are 10039-56-2 and 7681-53-0, respectively. We have encountered many customers who want to purchase anhydrous NaH2PO2, but in actual production, anhydrous powdered products do not exist. So, does sodium hypophosphite contain water?

Currently, the commonly used NaH2PO2.H2O monohydrate has a content of 101-103%. We might ask, why is the content higher than 100%? This question is complex and difficult to answer in detail here. Anhydrous sodium hypophosphite can only exist briefly in the laboratory because it is too dry and absorbs water extremely quickly, making it unsustainable for industrial production, let alone preservation. Even with vacuum packaging, anhydrous disodium hydrogen phosphate is extremely fragile during transportation, thus its existence is largely meaningless. Currently, NaH2PO2.H2O is actually used in industrial production.

In the production of many chemicals, a large portion of inorganic salts containing Na and K elements contain water of crystallization. Without water of crystallization, a solid cannot be formed. The characteristics of this chemical raw material are closely related to the characteristics of the elements it contains. Water of crystallization is not water in the usual sense; the ratio of NaH2PO2 to H2O molecules is not 1:1, but rather NaH2PO2/H2O>1.

NaH2PO2.HO does not necessarily contain a large amount of water, and anhydrous powder is not necessarily better than the monohydrate. Currently, both industrial-grade and electronic-grade sodium hypophosphite are monohydrates. Anhydrous powder, due to its high hygroscopicity, cannot be mass-produced industrially and has little practical significance. A NaH2PO2.H2O content of 101-103% is the main specification currently used.