Platinum color changes

During the reaction the color of the platinum complex changes from yellow to pale orange. Excess (AlMe,)2 can be removed under reduced pressure. 

From these equations it can be seen that each mole of water requires one mole of I2. In a visual endpoint Karl Fischer titration, a sample is titrated with the Karl Fischer reagent until a permanent iodine color (indicating that all water has been reacted) is observed. Because of other reaction products, the color change is usually from a yellow to a brownish color, which may be difficult to detect visually. Highly colored samples may affect the visual end point as well. A much sharper end point, known as the dead stop end point, can be obtained if the titration is done electrometrically. Here, two small platinum electrodes dip into the titration cell, a small constant voltage is impressed across these electrodes, and any current that flows is measured with a galvanometer. At the end point of the titration the current either goes to a minimum or else increases suddenly from nearly zero. Commercially available Karl Fischer instruments incorporate semiautomatic microprocessors based on this principle. 

Scheme12 Color change in a solution of the NCN-pincer platinum complex upon reversible binding with S02 gas (R = H, Fr chet dendron X = halogen) see also Fig. 7...

During the preparation of the composite containing PLA, cls-Pta2Cl2 and DOXO, a distinctive color change to Intense purple was observed (2 ). In view of the enhanced anticancer activity shown by this composite In animals over those containing the separate drugs. It was decided to Isolate and characterize the purple material, believed to be a chemical complex of the platinum with DOXO and. In addition, to Investigate the efficacy of this complex In to vivo experiments. 

Formula weight 486.0. Pure yellow crystals dissolve with difficulty in water insoluble in alcohol. The color changes in the presence of the other platinum metals in the same way as does that of (NH4)2PtCla. Solubility in water ... 

The cyclic voltammograms and the changes that occur to them during repetitive cycling are similar to those of 3-methylthiophene oxidation in acetonitrile. When a platinum electrode is used, the color change (red-blue) due to the redox transformation of poly (3-methylthiophene) is easily visible. A visual inspection also reveals that the electropolymerization reaction starts at the three-phase junction, as theoret-... 

The copper wire, like the platinum wire, changed to a glowing red color when heated. Upon cooling, a new substance, black copper(II) oxide, had appeared. 

The oscillations in most demonstration experiments produce periodic color changes. However, other properties of the solution, like the electrical potential, oscillate as well. This is due to changes in the concentrations of the redox active species. The electrical potential changes can be observed by measuring the potential of a platinum electrode versus a reference electrode. The voltage oscillates in phase with the color changes. The range of oscillations in the classic Belousov-Zhabotinsky reaction is about 200 mV. If the solution is poured in a petri dish and left unstirred, mosaic patterns appear as spatial oscillations. 

A solution containing 26.3 mg of vitamin 6,2 in 15 ml of water was shaken with 78 mg of platinum oxide catalyst and hydrogen gas under substantially atmospheric pressure at 25 C for 20 hours. Hydrogen was absorbed. During the absorption of hydrogen the color of the solution changed from red to brown. The solution was separated from the catalyst and evaporated to dryness in vacuo. The residue was then dissolved in 1 ml of water and then diluted with about 6 ml of acetone. 

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