Copper, iodometric determination

Eyler,26 who determined the copper iodometrically after precipitation of copper carboxymethylcellulose phosphates interfered with this analysis. A more satisfactory precipitating agent was found to be uranyl nitrate hexahydrate,26 though earlier investigations21 had shown that carboxymethylcellulose precipitates more than the theoretical amount of uranium. Mention should be made of the original analytical method developed by Kalle and Co.,26a in which the cellulose ether was determined by dichromate oxidation. 

These reactions are used in quantitative analysis for the iodometric determination of copper. 

The concentration of copper in a sample may be determined by using an iodometric titration or by atomic absorption spectrometry. In each of the following examples, calculate the cost of the assay (assume that the charge for the analyst s time is 50 per hour) ... 

Dimethoxycopper(II) is a moisture-sensitive blue compound that is insoluble in common organic solvents. It can be recrystallized from MeOH/NH3 to give a microcrystalline solid. Analysis of copper by iodometric titration provides a quick routine purity determination for dimethoxycopper(II).8 The complete removal of residual chloride from dimethoxycopper(II) is not easily achieved the most likely impurity is CuCl(OMe), which is a green compound.5 Dimethoxycopper(II) must be washed thoroughly as described above to minimize contamination by CuCl(OMe), and is obtained in >98% purity by this procedure (on the basis of the C, H, Cl, Cu, and Li analyses). IR (KBr, cm 1) 2917(vs), 2885(vs), 2806(vs), 1436(w), 1150(w), 1052(vs), 528(vs), 438(s). 

A number of important methods are based on the oxidation of sugars by ferricyanide ion in alkaline solution. The method is open to the same objections as the copper reduction methods, namely, the lack of a stoichiometric reaction and the dependence of the method on arbitrarily chosen conditions. The ferricyanide may be used to titrate the sugar solution directly by the use of picric acid or of methylene blue as an indicator. Or, the reduced ferrocyanide may be precipitated as the zinc salt, and the excess ferricyanide determined iodometrically. The Hagedom-Jensen method and the Hanes modification utilize the latter procedure. In the Folin-Malmros micro method, Prussian blue is formed and determined colorimetrically. Extensive application of the ferricyanide method has been made in the determination of the diastatic power of amylase preparations and in blood analysis. 

According to Analysis of Metals (1) a method similar to that for copper can be used. Two g of chips are combusted at 1400 to lASO C in an oxygen stream in a tube furnace. The combustion boat is filled with the nickel chips, which are then covered by 2 g of copper chips. The determination of sulphur dioxide is carried out by iodometric titration. 

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