โ Scribed by V.T. Athavale; T.P. Ramachandran; M.M. Tillu; M. Vaidya
No coin nor oath required. For personal study only.
A method has been developed for the spcctrophotomctric dctcrmination of indium in uranium and thorium metals and their salts in the range 0.x to x0 p.p.m.
According to SANDELL 1, mdium can be separated by oxinc-chloroform extraction at pa 3.5, but clemcnts such as gallium, aluminium, cobalt, nickel, thallium, tin, molybdenum, iron, vanadium and bismuth interfere by giving colourcd extracts.
A method has been describecl by MAY AND HOFFMAN' in which indium and other metals listccl above are first extracted with oxinc-chloroform solution at per 4 in presence of ammonium citra.tc. After the oxinates have been clecomposcd. indium, aluminium, gallium, thallium and bismuth are extracted with chloroform from an aqueous citrate-cyanide solution at prr 8.5 in presence of cupferron and dithizone. The metals are then transferred to the aqueous solution by shaking the extracts with ~'i: nitric acid. Finally, indlum is determmcd in alkaline solution containing potassium cyanide and ammomum cyanide with dithlzonc-chloroform.
It is possible to determine IO pg of inclium in presence of IO mg of copper, zinc and lead; bismuth, tin and thallium interfere.
The oxine-chloroform method cannot be used to separate indium from uranium and thorium at pxi 4; the recovery 1s not quantitative.
From an alkaline solution containing ammonium citrate ancl potassium cyanide inclium is extracted along with lead, bismuth, thallium and tin4 by a solution of clithizonc m chloroform. The optimum prr of extraction is 8.3-9.6'. Uismutlr if present in large amounts can bc removed by prior extraction with dlthizone-chloroform at PII 3.5-4. Stannic tin is not extracted 'along with indiuma*d.
Chtru. AC&, 22 (~gfio)
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