Nickel dimethylglyoxime paper

Place a drop of the neutral or acetic acid test solution upon nickel dimethylglyoxime paper, and almost dry by waving over a flame. Immerse the paper in dilute hydrochloric acid until the surface surrounding the fleck becomes white, and then wash the paper with cold water. A pink to red spot remains, depending upon the quantity of palladium present. The acid-stable palladium dimethylglyoxime at the site of the fleck protects the underlying red nickel dimethylglyoxime from attack by the acid. 

Reagent Nickel dimethylglyoxime paper. Filter paper (S S 589 g) is bathed in cold saturated alcohol solution of dimethylglyoxime. After drying, the paper is placed in 2 iV Ni(N03)2 that has been made barely ammoniacal nickel dimethylglyoxime precipitates. After thorough washing with water, the paper is bathed briefly in alcohol and dried. 

A useful spot test utilizes the fact that a suspension of red nickel dimethylglyoxime in water when treated with a neutral or acetic acid solution of a palladium salt yields the yellow palladium dimethylglyoxime, which is sparingly soluble in dilute acids. The test is best performed with dimethylglyoxime paper the latter is prepared as follows. Immerse drop-reaction paper in a 1 per cent alcoholic solution of dimethylglyoxime, dry, then immerse again in a solution of 05m nickel chloride rendered barely ammoniacal. The nickel complex precipitates wash thoroughly with water, immerse in alcohol and dry. 

It is advisable to saturate the reagent (a mixture of the ketoxime and ammoniacal nickel solution) with nickel dimethylglyoxime, and to carry out the test as a spot reaction on filter paper. 

Procedure. Filter paper is impregnated with the reagent solution and dried. According to the amount of hydroxylamine present, a more or less intense red fleck or ring of nickel dimethylglyoxime is formed on the yellow paper when spotted with a drop of the test solution. 

In another method of testing for nickel in alloys, the surface is freed of grease with ether, and a drop of a solution of 0.5 g dimethylglyoxime in 5 ml 98 % alcohol and 6 ml ammonia is added. A pink fleck of nickel dimethylglyoxime forms and may be made clearly visible by rubbing a piece of filter paper on the stain. The test is more sensitive if the portion of the surface to be tested is oxidized by the action of a blowpipe flame before treating it with the reagent. ... 

Electrography — Electrography, introduced independently by A. Glazunov and H. Fritz, is an obsolete technique for the direct electrochemical analysis of solid materials. The principle is that a solid specimen is pressed on a paper which is soaked with an electrolyte solution. By anodic oxidation of the surface of the solid specimen the reaction products (e.g., nickel(II) ions) react with a reagent in the paper (e.g., dimethylglyoxime) to give colored reaction product (red in case of nickel(II) and dimethylglyoxime). This produces a print that clearly shows the distribution of the reactive element (nickel, in our example) on the surface of the specimen. 

Separation of Pd with a collector. To the sample solution (-100 ml) in 0.1 M HCl, containing not more than 50 pg of Pd and heated to 80°C, add a macerated filter paper and 1 ml of 5% oxalic acid solution. Keep the solution at 80°C for 1 h, then allow it to cool. Filter off the precipitate of elemental gold and silver chloride together with the paper. To the filtrate add successively 2 mg of nickel (as its sulphate solution), 2 ml of 20% potassium sodium tartrate solution [to mask Fe(IIl), Al, Ti, etc.], 2 g of sodium acetate, 1 ml of 0.1 A/ EDTA, and 2 ml of the H2Dm solution (pH -6.5). After 30 min, filter off the precipitate of nickel- and palladium dimethylglyoximates. Wash the precipitate from the filter paper into a beaker, add 1 ml of cone. HCl, and evaporate to 5-10 ml, depending on the quantity of Pd in the solution. 

Pores and active defects in nonmetallic coatings can be revealed by color indication or deposit fomation. On nickel substrates, dimethylglyoxime, or steel, potassium ferricyanide (ferroxyl test) indicator can be applied to surface on filter paper while substrate is made the anode. Alternatively, a substrate immersed in acidic copper sulfate can be made the cathode to form copper nodules at conductive coatings defects. 

Figure 33 shows the result of a separation procedure for lead, copper, iron and nickel carried out in this way. Copper is fixed as sulfide on the paper disk, iron and nickel washed into the ring zone and then revealed respectively in individual sectors by reaction with potassium cyanoferrate(II) and dimethylglyoxime. 

Procedure. A drop of the test solution and one of 1 % alcoholic dimethylglyoxime solution are placed on filter paper and held over ammonia, or they are mixed on a spot plate and a small drop of dilute ammonia added. The formation of a red fleck or circle on paper, or of a precipitate or color on the spot plate, indicates the presence of nickel. 

The procedure described on page 325, employing paper impregnated with dimethylglyoxime, can be used for the detection of small amounts of nickel in the presence of much cobalt, copper or manganese. 

Procedure. A drop of the test solution is placed on paper impregnated with dimethylglyoxime. The paper is then immersed in a bath of dilute ammonia, and kept in gentle motion. The colored dimethylglyoxime compounds of cobalt and copper are dissolved the red fieck due to nickel remains on the white paper. 

The paper is immersed in 1 % ethanolic dimethylglyoxime, dried, immersed in 5 % aqueous ammonia containing 3 g/1 of a wetting agent and applied to the test surface. A pale-red color indicates the presence of nickel. e) Silver... 

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