is Na2Cr2O7 a primary standard in volumetry ?

In volumetric analysis,standard solution is a solution whose concentration is known and it is prepared by taking a known weight of substance called as primary standard and dissolves it in a given volume of water.
Thus primary standard substances are those substances whose standard solutions can be prepared directly by dissolving an accurately weighed amount of the substance in a known volume of water.For ex-- K2Cr2O7,Mohr’s salt etc.However Na2Cr2O7 cannot be used as a primary standard as it is hygroscopic in nature so it cannot be accurately weighed in air, thereby not fulfill one of the requirements of the substance to be considered as primary standard which is --substance must not be hygroscopic and must be capable of being dried without decomposition.