NA2H is the chemical formula for sodium hydride, a strong reducing agent commonly used in organic synthesis reactions. It is a white crystalline solid that reacts violently with water to release hydrogen gas. Sodium hydride is also used in the synthesis of pharmaceuticals and other organic compounds.
The formula for disodium ammonium phosphate is Na2H(NH4)(PO4).
Sodium phosphate, usually listed as an ingredient on food labels, can be referring to either monosodium phosphate, disodium phosphate, or trisodium phosphate. It is usually an emulsifier (thickener) or a preserving agent. Disodium is the one most commonly used.