PLASMOCHIN AS A REAGENT IN INORGANIC ANALYSIS——III. DETECTION OF IODATE AND PERIODATE IONS
SHEN Nai-Kuei; HSIU Mei-Gin Department of Chemistry, Bang-Bu Medical College
Plasmochin in the presence of 1 N perchloric acid and under heating in boiling water bath reacts with iodate and periodate ions to give a red-violet coloration which is insoluble in ordinary organic solvents (19 organic solvents have been tested). The optimum conditions and selectivity of the colour reaction have been investigated in detail. The identification and concentration limits in centrifuge tube have been found experimentally. The limits of proportion of IO_3~- and IO_4~- with 19 cations and 25 anions have also been determined, and in most cases, they neither affect the reaction nor decrease the sensitivity even present in 500-fold amounts. However, silver, mercurous and mercuric ions lower the sensitivity. Cerium (IV), CrO_4~(2-), Au~(3+), Fe~(2+), Fe~(3+), Sn~(2+), VO_3~- as well as most reducing anions interfered with the detection. Among the interfering ions, Ce~(4+), Au~(3+) and Fe~(3+) can be separated out by ammonium hydroxide, CrO_4~(2-) by perchromic acid-ether extraction, and VO_3~- by oxine-chloroform extraction. Procedures for detection of IO_3~- and IO_4~- even in the presence of the above mentioned interfering ions, have been devised. The results after separation are satisfactory and the recommended procedures are useful for detecting IO_3~- or IO_4~-.