As explained by Cox and Peters, anhydrous sodium hexachloroplatinate, which is yellow, tends to form the orange hexahydrate upon storage in humid air.

[2] Sodium hexachloroplatinate is obtained as an intermediate in the preparation of Pt complexes, often starting with the dissolution of platinum in aqua regia, giving hexachloroplatinic acid, which is then reacted with sodium chloride and evaporated, leaving the salt behind.

This compound also reacts with a base, such as sodium hydroxide, producing [Pt(OH)6]−2 ion.

[4] A 1.2 M solution of sodium hexachloroplatinate in D2O is the most commonly chosen reference compound for chemical shifts in 195Pt NMR.

The salt is chosen as it is commercially available at a lower price relative to other platinum compounds, and it possesses high solubility enabling quick acquisition of spectra.