Photometric determination of micro amounts of thiosulphate by means of its cyanolysis with lanthanum(III) as catalyst.
Lanthanum(III) has been found to catalyse the reaction of thiosulphate with cyanide. The effects of pH, reaction time and temperature, amount of cyanide and lanthanum, and order of addition of reagents have been investigated. Temperature has little effect in the range 10-30 degrees , but at both 35 degrees and 40 degrees the rate is noticeably faster. Reaction is complete at room temperature in 1.5 hr at pH 9.3-9.6, and in 3 hr at pH 9.1-9.6. The method can be applied to the determination of 1.0 x 10(-5)-6.0 x 10(-4)M thiosulphate, with a relative standard deviation of 0.3% for 4 x 10(-4)M thiosulphate.
Koh
T
T
Department of Chemistry, Faculty of Science, Tokai University, Hiratsuka, Kanagawa, 259-12, Japan.
Miura
Y
Y
Katoh
M
M