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INDIUM
Natural Abundance, Stable Isobars
In113, 4.33%, bCd113
aIn115, 95.67%
Indium metal, indium trichloride, indium tribromide, and indium triiodide were used as charge material in the early separations of indium isotopes. The triiodide proved superior in these separations, but still had three undesirable features: it was very deliquescent, it produced very strong bands of 1+ ions during operations, and its preparation required a large amount of relatively expensive iodine. In an effort to minimize these features, InI  was synthesized for use as a feed material. Use of InI  resulted in a 50% increase in indium ion output, a reduction in the time required to attain operating pressure, and a net saving in charge material cost. The usual charge consists of 400 g InI in a style X-5 stainless steel charge bottle.
In the synthesis of InI, indium metal is placed in a flask and heated over a flame until melted (mp, 155° C). Iodine is then added, a small amount at a time, with frequent shaking of the flask, until no more brown fumes emanate after an addition of iodine. (This point is reached when the layer of molten InI covering the molten indium prevents iodine crystals coming in contact with the indium.) Instead of reacting, the iodine is volatilized and passes out of the flask as a purple vapor. At this point the liquid InI is decanted into a stainless steel tray where it quickly solidifies. Since InI is somewhat hygroscopic, the resulting cake is broken out of the tray immediately and bottled. This compound can be produced at the rate of 1 kg/hr by adding iodine or indium as needed in a continuing operation.
Indium and its compounds are considered toxic. A fume hood with good exhaust ventilation, rubber gloves, safety glasses, and respirators, if dusting occurs, should be used when handling indium and its compounds.
aIn115, is radioactive with a half-life of 6 × 1014 years.
bCd113, natural abundance 12.26%, is radioactive with a half-life of > 1015 years.  
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