This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Phosphate of sodium should be kept in well-stopped bottles, in a cool place. Large, colorless, transparent, monoclinic prisms, speedily efflorescent and becoming opaque on exposure to air, odorless, having a cooling, saline and feebly alkaline taste, and a slightly alkaline reaction. Soluble in water, insoluble in alcohol.
Five parts by weight of phosphate of sodium in 95 parts of distilled water. Filter. Specific gravity 1.055 at 15° C. Proportion 100 to 1. It is not advisable to make a 10 per cent, solution, as crystals would separate at ordinary temperature and cling to the sides of the bottle. A 5 per cent, solution is the most convenient. We refer to page 24 of this work, "Test for Phosphoric Acid or Phosphates" from where will be learned that when phosphate of soda enters as a component, the water must or should be free of iron, lime and magnesia, to prevent turbidity. Still, phosphate of soda is a component of quite a number of mineral waters, and will also be found a constituent of the appended formulas for artificial combinations, besides iron, magnesia and lime. The combinations it may form keep in solution when the water is charged with carbonic acid gas, and then cause no turbidity, as carbonic acid acts as a solvent. But its influence must be remembered when the gas pressure has disappeared; then it will form insoluble compounds and cause turbidity. And this occurrence is frequently experienced in beverages which contain phosphoric compounds, the water employed containing iron, lime or magnesia, and no sufficiency of carbonic acid gas. Therefore we have advocated the employment of pure water for all saccharine beverages, and recommend a careful impregnation with carbonic acid gas for artificial mineral waters, when those components are present. (See also "Preservatives " for mineral waters.)