Blue tungsten oxide is acidic oxide. It can’t be soluble in water, slightly soluble in acid. Blue tungsten oxide can react with alkali to form the corresponding soluble tungstate, so blue tungsten oxide can be soluble in alkali.
Solubleness is the degree to which a substance can be dissolved. If a solute is dissolved in a solvent well, we say that the substance is soluble. If it is not much dissolved, it is said that the substance is slightly soluble. If it is difficult to dissolve, then it is said that this material is insoluble or difficult to dissolve. In a certain temperature, the solubility of a solid substance in the 100g solvent to reach saturation state is the quality of the dissolved.