Chinese Journal of Applied Chemistry ›› 1984, Vol. 0 ›› Issue (1): 13-20.

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GRAVMETRIC DETERMINATION OF SCANDIUM WITH BENZILIC ACID

Liang Shuquan(Shu-Chuan Liang), Wang Zhi   

  1. Institute of Chemitsry, Academia Sinica, Beijing
  • Received:1983-09-30 Revised:1983-10-25 Published:1984-03-10 Online:1984-03-10

Abstract: This paper reports the use of benzilic acid [(C8H5)2 C(OH) COOH]crystals as the precipitant for scandium, instead of its sodium salt or am-monium solution. By adding the crystals to acidic solution of scandium andthen adjusting the acidity to pH 2.0-2.5, pure scandium benzilate can beobtained. This mode of precipitation prevents the formation of scandiumbasic salt and/or hydroxide. From the thermogravigram of the precipitateso obtained, it has been shown that precipitates dried at 160° and 140℃ cor-respond to Sc[(C6H5)2C(OH)COO]3 and its monohydrate respectively. From592℃ upward, the precipitate becomes scandium oxide. To ensure completeconversion, 650℃ should be used for ignition. Quantitative precipitation ofscandium benzilate can be achieved from solutions of pH 2.0-5.0.Beyond pH5, the precipitate hydrolyzes to basic salt. The amount of benzilicacid needed for quantitative precipitation is 1.5 to 5 fold of the theoretical value. The interference of iron(Ⅲ) can be avoided by (a) reducing to ferrousstate with ascorbic acid, or(b) masking with citric acid--triethanolaminemixture. The latter masks aluminum (Ⅲ) too. Hydrogen peroxide maskingeliminates the interference of titanium(Ⅳ). Yttrium(Ⅲ), larithanum (Ⅲ)and cerium (Ⅲ) benzilates begin to precipitate at pH 1.3, 3.1 and 2.6,respectively. Therefore it is impossible to determine scandium in theirpresence, unless separation is carried out beforehand.