Silver—continued

Let us say that we have the Red Stone multiplied to a strength of one part to one hundred parts metal. Take one hundred parts of pure silver metal and melt it in a crucible. When it is completely molten, take one part of the Incerated Red Stone and form it into several small balls or pills. Slowly add one pill at a time to the crucible and allow it to fuse with the silver. Continue adding the small pills until you have added the full one part. 

Figure 11.36 By extending the polyol reaction for a ven time period, various polyhedral shapes capped with 100 and 111 faces can be obtained in high yield, a) A schematic of the nucleation and growth process, in which silver continuously deposits onto the 100 faces to eventually result in a completely 111 -bound octahedron, b to f) SEM images of cubes, truncated cubes, cuboctahedra, truncated octahedra, and octahedra, respectively (scale bar 100 nm). Reproduced with permission from reference [91]. (2006) Wiley-VCH Verlag GmbH Co. KGaA.

Fig. 9.12. Silver continuous centrifuge. Courtesy CF I Engineers, Inc., Denver, CO.)...

Siher(Il) oxide, AgO, is a black solid, Ag Ag 02, obtained by anodic or persulphate oxidation of an AgNOs solution. Continued anodic oxidation gives impure Ag203. Argentates, e.g. K.AgO, containing silver(I) are known. 

Introduce a solution of 15 g. of the diazo ketone in 100 ml. of dioxan dropwise and with stirring into a mixture of 2 g. of silver oxide (1), 3 g. of sodium thiosulphate and 5 g. of anhydrous sodium carbonate in 200 ml. of water at 50-60°. When the addition is complete, continue the stirring for 1 hour and raise the temperature of the mixture gradually to 90-100°. Cool the reaction mixture, dilute with water and acidify with dilute nitric acid. Filter off the a-naphthylacetic acid which separates and recrys-talhse it from water. The yield is 12 g., m.p. 130°. 

Ethyl a-naphthylacetate is prepared as follows. To a solution of 10 g. of the diazo ketone in 150 ml. of ethanol at 55-60°, add a small amount of aslurry of silver oxide, prepared from 10 ml. of 10 per cent, aqueous silver nitrate and stirred with 25 ml. of ethanol. As soon as the evolution of nitrogen subsides, introduce more of the silver oxide and continue the process until all the slurry has been added. Reflux the mixture for 15 minutes, add 2-3 g. of decolourising carbon, filter and evaporate the alcohol on a water bath. Distil the residue and collect the ethyl a-naph-thylacetate at 176-178°/ 1 mm. the yield is 9 g. 

Alternatively, treat a solution of 3 9 g. of the 6is-diazo ketone in 50 ml. of warm dioxan with 15 ml. of 20 per cent, aqueous ammonia and 3 ml. of 10 per cent, aqueous silver nitrate under reflux in a 250 or 500 ml. flask on a water bath. Nitrogen is gently evolved for a few minutes, followed by a violent reaction and the production of a dark brown and opaque mixture. Continue the heating for 30 minutes on the water bath and filter hot the diamide of decane-1 lO dicarboxyhc acid is deposited on cooling. Filter this off and dry the yield is 3 -1 g., m.p. 182-184°, raised to 184-185° after recrystallisation from 25 per cent, aqueous acetic add. Hydrolyse the diamide (1 mol) by refluxing for 2-5 hours with 3N potassium hydroxide (4 mols) acidify and recrystaUise the acid from 20 per cent, acetic acid. The yield of decane-1 10-dicarboxyhc acid, m.p. 127-128°, is almost quantitative. 

Uses. The principal use for sodium thiosulfate continues to be as fixative in photography (qv) to dissolve undeveloped silver haUde from negatives or prints. In appHcations where rapid processing is requited, such as the processing of x-ray film, sodium thiosulfate has been largely replaced by ammonium thiosulfate. 

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