Potassium ions, copper composite electrodes

An experimental example can be found in [13]. The diffusion coefficients of electrons and potassium ions in copper(II) hexacyanoferrate(II) composite electrodes were determined using impedance spectroscopy. Composite electrodes are mixtures of graphite and copper hexacyanoferrate (Cu hcf) powder embedded in paraffin. The diameter of the Cu hcf particles amounted to about 30 xm. The diffusion region of electrons is limited by the size of these particles. For the first time, a diffusion of electrons in hexacyanoferrates could be detected. The diffusion coefficient obtained was 0.1 cm s . ... 

Elemental composition Cu 64.18%, Cl 35.82%. Copper(I) chloride is dissolved in nitric acid, diluted appropriately and analyzed for copper by AA or ICP techniques or determined nondestructively by X-ray techniques (see Copper). For chloride analysis, a small amount of powdered material is dissolved in water and the aqueous solution titrated against a standard solution of silver nitrate using potassium chromate indicator. Alternatively, chloride ion in aqueous solution may be analyzed by ion chromatography or chloride ion-selective electrode. Although the compound is only sparingly soluble in water, detection limits in these analyses are in low ppm levels, and, therefore, dissolving 100 mg in a liter of water should be adequate to carry out aU analyses. 

Other types of electrodes have been designed to measure the concentrations of ions other than H30. The simplest example of such an ion-selective electrode is a metal wire, which can be used to detect the concentration of the corresponding metal ion in solution. Silver and copper wires can be used reproducibly in this way to determine the concentrations of Ag and Cu, respectively. Still other electrodes have been developed to detect specific ions. For example, glasses of chemically modified composition are used to construct membrane electrodes to determine potassium and sodium ions or halogen ions. 

Recently, a novel graphene-copper nanoparticle composite was prepared by the in situ chemical reduction of a mixture containing graphene oxides and copper(II) ions using potassium borohydride as a reductant. It was mixed with paraffin oil and packed into one end of the fused capillary to fabricate microdisk electrodes for sensing carbohydrates [14]. The results indicated that copper nanoparticles with an average diameter of 20.8 nm were successfully deposited on the graphenes to form a well-interconnected hybrid network. 

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