PREPARATIONS 115 Potassium Antimonyl Tartrate (Tartar Emetic). C 4 H 4 O 6 KSbO, ^H 2 O. Tartaric acid is noteworthy for (a) the excellent way in which the majority of its salts crystallise, and (6) the frequent occurrence of salts having mixed cations. Examples of the latter are sodium potassium tartrate (or Rochelle salt), C 4 H 4 O 6 NaK, used for the preparation of Fehling's solution (p. 525), godium ammonium tartrate, C 4 H 4 O 8 NaNH 4 , used by Pasteur for his early optical resolution experiments, and potassium antimonyl tartrate (or Tartar Emetic), C 4 H 4 O 6 K(SbO). The latter is prepared by boiling a solution of potassium hydrogen tartrate (or "cream of tartar") with antimony trioxide, CH(OH)-COOK CH(OH)-COOK 2 I + Sb 2 O, -* 2 I 4- H 2 O CH(OH)-COOH CH(OH)-COO(SbO) when the acidic hydrogen atom is replaced by the monovalent antimonyl (Sb:O) radical.* Required: Potassium hydrogen tartrate, 5 g.; antimony trioxide, Sg-Add 5 g. of potassium hydrogen tartrate and 5 g. of antimony
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