Potassium antimonyl tartrate, preparation

Tartaric acid is noteworthy for a) the excellent way in which the majority of its salts Crystallise, and h) the frequent occurrence of salts having mixed cations. Examples of the latter are sodium potassium tartrate (or Rochelle salt), C4H40 NaK, used for the preparation of Fehling s solution (p. 525), sodium ammonium tartrate, C4H OaNaNH4, used by Pasteur for his early optical resolution experiments, and potassium antimonyl tartrate (or Tartar Emetic), C4H404K(Sb0). The latter is prepared by boiling a solution of potassium hydrogen tartrate (or cream of tartar ) with antimony trioxide,... 

Potassium antimonyl tartrate solution. In a 250-mL Erlenmeyer flask, dissolve 0.45 g of potassium antimonyl tartrate in about 50 mL of distilled water. Swirl gently until dissolved, and then dilute to 100 mL and swirl to make homogeneous. Prepare just prior to the run. 

Three and four-tenths grams of antimony trisulfide is prepared by passing hydrogen sulfide into a solution of 6.6g potassium antimonyl tartrate (4.5g of the trichloride or 2.9g of the trioxide may be used instead) in 2N hydrochloric acid until precipitation is complete. 

Standard antimony solution 1 mg/ml. The solution may be prepared either from potassium antimonyl tartrate (Section 7.2.1) or in the following manner. Dissolve 0.1000 g of powdered antimony metal in 25 ml of cone. H2SO4. Dilute the cooled solution with water while stirring, cool, and make up to 100 ml in a standard flask. Working solutions are obtained by suitable dilution of the stock solution with 0.5 M H2SO4. 

Potassium Antimonyl Tartrate—Tartarated antimony—Tartar emetic—Antimonii et potassii tartras (U. S.)—Antimonium tar-taratum (Br.)—(SbO)KC.H.O —323—is prepared by boiling a. mixture of 3 pts. SbiO. and 4 pts. HKCiH.O.in H.O for an hour. 

Mix together 100 ml ammonium molybdate, 250 ml sulphuric acid, 100 ml ascorbic acid, and 50 ml potassium antimonyl-tartrate solutions. Prepare this reagent for use and discard any excess. Do not store for more than about 6 hr. The above quantity is suitable for about 50 samples. 

POTASSIUM ANTIMONYL-TARTRATE SOLUTION Prepare as described in II.2.I,E.4. 

Mixed Reagent - Add successively with a graduated cylinder and mix after each addition 50 ml sulphuric acid (6.5), 15 ml ammonium molybdate solution (6.3), 30 ml ascorbic acid solution (6.2) and 5 ml potassium antimonyl tartrate solution (6.4). Prepare fresh daily. 

Weigh out accurately 2.0 g of the purest potassium antimonyl tartrate, dissolve and make up to 250 cm with water. Safely pipette 50.0 cm of the solution into a conical flask add 20 cm of a saturated solution of sodium bicarbonate and 2 cm of freshly prepared starch solution. Titrate with standardised 0.05 M iodine solution until first... 

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