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.
Tartaric acid is prepared from crude tartar (acid tartrate of potassium), which is met with either free or in combination with bases especially in grapes, also in sumach berries, tamarinds, pineapples, and other acidulous fruits.
Tartaric acid crystals are transparent, colorless prisms or tables, inodorous, of strongly acid but agreeable taste, not deliquescent in the air, easily soluble in water (0.6 parts), in two parts of 85 per cent, alcohol. The solution has a pure acid taste, and gradually spoils while keeping, if not preserved like the solution of citric acid. It also, like citric acid, converts cane-sugar into invert-sugar. It is used to acidify carbonated beverages, for seidlitz powders, and to a great extent in many other trades for manufacturing purposes. In American commerce tartaric acid is usually found in the state of powder, hut we suggest to buy and employ only the crystallized form, as it is less liable to be adulterated than if in powder.
Tartaric acid often contains lime. When this is the case it fails to dissolve in alcohol, in three parts of which it should completely dissolve.
A solution in 10 parts of water should not be precipitated or colored dark by hydro-sulphuric acid.
Dissolve one pound of tartaric acid crystals in two pints cold and filtered water. Stir with a wooden spatula or shake in a bottle until dissolved; filter and refilter before use. If boiling water is poured on the crystals they dissolve immediately without shaking. Use no metallic vessels or spatulas. Keep well-stoppered in a glass bottle ready for use. One fluid ounce of this solution represents one-half ounce of tartaric acid.
For some beverages, especially for fruit syrups, the fruits of which contain tartaric acid, or for economical reasons, it is oftentimes preferred to use a mixture of citric and tartaric acid solution in equal or other suitable portions: Citric acid eight ounces, tartaric acid eight ounces, cold filtered or boiling water as before two pints. A fluid ounce of this solution also represents one-half ounce of the acids, mixed in equal portions. The partial use of citric acid improves the beverage in taste, and is preferable to using tartaric acid alone. The latter imparts to the beverage the natural acidulous taste, but the addition of some citric acid refines this taste and many manufacturers use citric acid exclusively.