Silver, colloidal cyanide

K Kneipp, H Kneipp, G Deinum, I Itzkan, RR Dasari, MS Feld. Single-molecule detection of a cyanide dye in silver colloidal solution using near-infrared surface-enhanced Raman scattering. Appl Spectrosc 52 175-178, 1998. 

The acute toxicity of metallic silver and water-soluble compounds is moderate. The oral LD50 in mice for colloidal silver was 100 mg kg and relatively similar for the water-soluble compounds silver nitrate (50-129 mg kg ) and silver cyanide (LD50 in rats, 125 mg kg ). Silver nitrate appears much less toxic in rabbits by the oral route (800 mg kg ). The insoluble silver oxide was reported to exhibit an LDlo of >2gkg Mn rats. 

Donnan, from Laplace s theory of the internal pressure of liquids, arrived at a theory of negative surface tension which was supposed to explain why substances disperse to form colloidal rather than true solutions, a minimum size of particle being stable. Donnan and Barker investigated adsorption (see p. 742), Donnan and Le Rossignol the kinetics of the reaction between ferri-cyanide and iodide (see p. 660), and Donnan and Miss K. A, Burke the kinetics of the reaction between silver nitrate and alkyl iodides. 

The formation of (II) provides a quite selective spot test for palladium. Gold must be removed prior to the test because it will cause the development of a deep ruby red in the spot plate test and a diffused violet spot on the paper, apparently due to the reduction of the gold ions to the colloidal metal. Interference may also arise from 0s04 , Os+, Ru+, and RuCle ions because they have distinct self-colors. Mercurous ion causes partial interference by the reduction of part of the palladium to the elementary state, but a positive response can still be seen. It is possible to detect I part of palladium in the presence of 200 parts of platinum or 100 parts of rhodium. Less favorable ratios should be avoided because of the color of these salts. No interference is caused by mercuric and iridic chloride, but free ammonia, ammonium ions, stannous, cyanide, thiocyanate, fluoride, oxalate, and tetraborate ions do interfere. Lead, silver, ferrous, ferric, stannic, cobaltous, nickel, cupric, nitrite, sulfate, chloride, and bromide ions do not interfere. 

Colloidal Silver Halides. — Hydrosols of silver chloride, bromide, and iodide were prepared by Lottermoser and E. v. Meyer 1[ by treating colloidal silver with the corresponding halogen. They were very sensitive to electrolytes. Another theoretically interesting method has also been worked out by Lottermoser. 11 It is based on the effect of silver nitrate on the silver halides. By this method have been prepared colloidal solutions of silver chloride, bromide, iodide, cyanide, ferro and ferricyanides, phosphate and arsenate. The reaction is particularly interesting because it can be followed by measurement. It may be carried out in two ways. Either a measured amount of silver nitrate is treated Avith dilute solutions of the alkali halides, or silver nitrate from a buret is added to a known amount of the halide. In the first there must be an excess of the silver ion and in the second an excess of the halide ion in order to obtain a hydrosol. If too much of the lesser constituent is added precipitation results. 

T. Linnert, P. Mulvaney, and A. Henglein, Photochemistry of colloidal silver particles the effects of nitrous oxide and adsorbed cyanide ion, Ber. Bunsen-Ges. Phys. Chem. 95, 838-841 (1991). 

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