Gold chloride blue

Prints that have been selenium-toned should only be reduced by the overall method, as the color of the print will change in the area that is bleached. Gold-chloride blue-toned prints should not be bleached at all, as the color will usually change to green-blue. For these reasons, it is better to reduce prints before toning. 

Test 1 Dilute 0.1 mL of the filtrate with 1 mL of water, and add one drop of gold chloride TS a violet blue color is produced at once. 

E. P. Alvarez 2 found that the pemitrates react with soln. of lead acetate (white precipitate), silver nitrate (white precipitate), mercurous nitrate (white precipitate with rapid decomposition), mercuric chloride (red precipitate), copper sulphate (blue precipitate), zinc and cadmium sulphates (white precipitate), bismuth nitrate (white precipitate), gold chloride (slight effervescence and escape of oxygen), manganous chloride (pink precipitate), nickelous chloride or sulphate (greenish-white precipitate), cobaltous nitrate and chloride (pink precipitate), ferrous sulphate (green or bluish-green precipitate), ferric chloride (red ferric hydroxide), and alkaline earth chlorides (white precipitates). The precipitates are all per-salts of the bases in question. 

If you intend to gold-tone a print for blue tones, do not add too much carbonate solution as it will make it difficult to secure a brilliant blue with gold chloride toner. 

One of the best methods to achieve blue-black tones is to use gold chloride. Not only does the gold chloride tone the print to various shades of blue, it also serves to protect the silver from degenerating. 

The concentration of the gold chloride affects the brilliance of the blue. Make the formula stronger by using less water or more gold chloride to increase the effect. 

Gold chloride solution reduced to finely divided metallic gold, which appears greenish-blue by transmitted light and brown by reflected light. 

The spot-test technique is as follows. Mix a drop of the neutral test solution with a drop of 0-33m. gold chloride solution in a micro crucible and warm. After a short time, the solution is coloured red or blue with colloidal gold. 

Add I cm3 of a 1% solution of gold chloride (HAuCU SHsO) to 100 cm3 of distilled water, bring to the boil, and add 2.5 cm3 of 1% sodium citrate solution. Keep the solution just boiling. After a few minutes observe the appearance of a blue coloration, followed shortly by the formation of a ruby-red gold sol. 

Stannous Oxide. Stannous oxide, SnO ((tin(II) oxide), mol wt 134.70, sp gr 6.5) is a stable, blue-black, crystalline product that decomposes at above 385°C. It is insoluble in water or methanol, but is readily soluble in acids and concentrated alkaHes. It is generally prepared from the precipitation of a stannous oxide hydrate from a solution of stannous chloride with alkaH. Treatment at controUed pH in water near the boiling point converts the hydrate to the oxide. Stannous oxide reacts readily with organic acids and mineral acids, which accounts and for its primary use as an intermediate in the manufacture of other tin compounds. Minor uses of stannous oxide are in the preparation of gold—tin and copper—tin mby glass. 

The elements are obtainable in a state of very high purity but some of their physical properties are nonetheless variable because of their dependence on mechanical history. Their colours (Cu reddish, Ag white and Au yellow) and sheen are so characteristic that the names of the metals are used to describe them. Gold can also be obtained in red, blue and violet colloidal forms by the addition of vtirious reducing agents to very dilute aqueous solutions of gold(III) chloride. A remarkably stable example is the Purple of Cassius , obtained by using SnCla as reductant, which not only provides a sensitive test for Au but is also used to colour glass and ceramics. Colloidal silver and copper are also obtainable but are less stable. 

FIGURE 14.17 A diaphragm cell tor the electrolytic production of sodium hydroxide from brine (aqueous sodium chloride solution), represented by the blue color. The diaphragm (gold color) prevents the chlorine produced at the titanium anodes from mixing with the hydrogen and the sodium hydroxide formed at the steel cathodes. The liquid (cell liquor) is drawn off and the water is partly evaporated. The unconverted sodium chloride crystallizes, leaving the sodium hydroxide dissolved in the cell liquor. 

Metal Coatings. Tellurium chlorides, as well as tellurium dioxide in hydrochloric acid solution, impart permanent and attractive black antique finish to silverware, aluminum, and brass. Anodized aluminum is colored dark gold by tellurium electro deposition. A solution containing sodium tellurate and copper ions forms a black or blue-black coating on ferrous and nonferrous metals and alloys. Addition of sodium tellurite improves the corrosion resistance of electroplated nickel. Tellurium diethyldithiocarbamate is an additive in bright copper electroplating (see Electroplating). 

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