The impurities occasionally present in commercial citric acid are salts of potassium and sodium, traces of iron, lead and copper derived from the vessels used for its evaporation and crystallization, and free sulphuric, tartaric and even oxalic acid.
Citric acid is also distinguished from tartaric acid by the fact that an ammonia solution of silver tartrate produces a brilliant silver mirror when boiled, whereas silver citrate is reduced only after prolonged ebullition.
In repeating and extending the experiments of Haiiy much later, Sir David Brewster discovered that various artificial salts were pyro-electric, and he mentions the tartrates of potash and soda and tartaric acid as exhibiting this property in a very strong degree.
Moderately strong nitric acid changes it into mucic, saccharic, tartaric and oxalic acids.
It is a white powder, almost insoluble in water, and when volatilized, condenses in two crystalline forms, either octahedral or prismatic. It is insoluble in sulphuric and nitric acids, but is readily soluble in hydrochloric and tartaric acids and in solutions of the caustic alkalies.
At the beginning of July when the berries have attained to an appreciable size - the specific gravity of the juice is very low; it contains very little sugar, but a good deal of acid, chiefly free tartaric acid and malic acid.
Doebner's preparation of mesotartaric acid, the internally compensated tartaric acid, (CH(OH) COOH)21 by oxidizing phenol with dilute potassium permanganate (Ber., 1891,.
In alkaline solution, potassium permanganate oxidizes it to inactive tartaric acid and carbon dioxide (0.
He recommended that yeast should be purified by cultivating it in a solution of sugar containing tartaric acid, or, in wort containing a small quantity of phenol.
Traces of bismuth may be detected by treating the solution with excess of tartaric acid, potash and stannous chloride, a precipitate or dark coloration of bismuth oxide being formed even when only one part of bismuth is present in 20,000 of water.