Characters. - In large red, transparent, four-sided tables; anhydrous.

Reactions and Solubility. - It fuses below redness; at a higher temperature is decomposed, yielding green oxide of chromium and yellow chro-mate of potassium, which may be separated by dissolving the latter in water. The bichromate dissolved in water gives a yellowish-white precipitate with chloride of barium, and a purplish red precipitate with nitrate of silver, and both these precipitates are soluble in diluted nitric acid. The solution also when digested with sulphuric acid and rectified spirit acquires an emerald green colour.

Peeparations in which Bichromate of Potassium is used.

Acidum Chromicum. Sodae Valerianas.

Test solution of Bichromate of Potassium, U.S.P. 1 in 10 of water.

Action. - In frogs it causes general feebleness of motion, respiration, and circulation, and sometimes convulsions. The nerve-centres are first excited and then depressed. The nerve-centres are affected before the nerves or muscles. The heart stops in diastole. In mammals it causes vomiting, diarrhoea, and bloody stools, great feebleness, and general clonic movements. In rabbits and guinea-pigs convulsions and paralysis occur, chiefly affecting the posterior limbs. Post mortem a red coloration of the muscles is observed, and the gastric and intestinal mucous membranes are congested.

Uses. - It has been used by Vulpian alternately with iodide of potassium and nitrate of silver in tabes dorsalis; and in doses of 1/2-1 1/2 grain it is said to be useful in cases of dyspepsia simulating cancer of the stomach.