Silver diethyldithiocarbamate

Silver diethyldithiocarbamate [1470-61-7] is a reagent commonly used for the spectrophotometric measurement of arsenic in aqueous samples (51) and for the analysis of antimony (52). Silver iodate is used in the determination of chloride in biological samples such as blood (53). 

Arsenic. Total arsenic concentration can be determined by reduction of all forms to arsine (AsH ) and collection of the arsine in a pyridine solution of silver diethyldithiocarbamate. Organoarsenides must be digested in acidic potassium persulfate prior to reduction. The complex that forms is deep red, and this color can be measured spectrophotometricaHy. Reduction is carried out in an acidic solution of KI—SnCl2, and AsH is generated by addition of 2inc. 

Silver diethyldithiocarbamate [1470-61-7] M 512.3. Purified by recrystn from pyridine. Stored in a desiccator in a cool and dark place. 

Merry and Zarcinas [33] have described a silver diethyldithiocarbamate method for the determination of arsenic and antimony in soil. The method involves the addition of sodium tetrahydroborate to an acid-digested sample which has been treated with hydroxylammonium chloride to prevent the formation of insoluble antimony compounds. The generated arsine and stib-ine react with a solution of silver diethyldithiocarbamate in pyridine in a gas washtube. Absorbance is measured twice at wavelengths of 600 and 504 nm. 

Interferences Metals or salts of metals such as chromium, cobalt, copper, mercury, molybdenum, nickel, palladium, and silver may interfere with the evolution of arsine. Antimony, which forms stibine, is the only metal likely to produce a positive interference in the color development with the silver diethyldithiocarbamate. Stibine forms a red color with silver diethyldithiocarbamate that has a maximum absorbance at 510 nm, but at 535 to 540 nm, the absorbance of the antimony complex is so diminished that the results of the determination would not be altered significantly. 

Reagents. Silver DDC Solution. A 0.5% solution of silver diethyldithiocarbamate in pyridine. This reagent should be stored in amber bottles. 

In a further method the sample is heated in a sealed tube for 5 min with a mixture (3 + 1) of magnesium and magnesium oxide, which converts all the arsenic into magnesium arsenide On decomposition by dilute sulphuric acid, arsine is evolved and is absorbed in a 0.5% solution of silver diethyldithiocarbamate (AgDDC) in pyridine. The colour produced has an absorption maximum at 560 nm and is proportional to concentration up to 20 fig of arsenic in 3 ml of solution. Alternatively, the arsine is oxidized by bromine and determined iodimetrically. 

TABLE 1. Recovery of arsenic employing wet digestion with 5 ml of 30% hydrogen peroxide and 5 ml of sulphuric acid with analyses by silver diethyldithiocarbamate and atomic absorption ... 

The hydrogen peroxide-sulphuric acid digestion seemed to provide the most consistent and complete recoveries of any of the wet digestive procedures examined, and coupled with the silver diethyldithiocarbamate colorimetric analysis resulted in quantitative arsenic recoveries from waste water samples. 

Arsine bubbled into the solution in the cuvette, reacting with silver diethyldithiocarbamate to form a colored complex compound according to the following equation ... 

Preconcentration of As(III) diethyldithiocarbamate on silica chemically modified with hexadecyl groups was examined [1]. Emulsion liquid membrane (made up of L113A surfactant, liquid paraffin as stabilizer and kerosene as solvent with HCl and KOH as external and internal phases) separation of As(III) and As(V) was applied prior to detection with silver diethyldithiocarbamate ( =510 nm) [2]. The method was applied to Cu ore and slagged ash. 

A 25-mL solution containing 500 ppb of arsenic (Ag3+) was stirred with 1 g of borohydride-form A-26 anion-exchange resin. The reaction vessel was connected to an absorption tube filled with a solution to absorb the volatile hydride of arsenic (i.e., arsine, AsH3). The absorption solution is made by dissolving 1 g of silver diethyldithiocarbamate (SDDC) in 200 mL of pyridine. The volatile arsine is complexed with the SDDC solution to give a colored solution, whose absorbance is... 

Gravimetric methods and chemical methods, such as colorimetric measurements based on the arsenic-molybdenum blue complex (1,2,3) and arsine generation in combination with silver diethyldithiocarbamate (4, 5, 6,7), have been used to measure arsenic in aqueous media. Various instrumental methods such as differential pulse polarography (8), heated vaporization atomic absorption (9), arsine generation in combination with atomic absorption spectroscopy (10, 11, 12) or non-dispersive atomic fluorescence spectroscopy (13), and optical emission spectroscopy (14) can be used to determine arsenic in aqueous solutions. 

Quantitative. Classically, silver concentration in solution has been determined by titration with a standard solution of thiocyanate. Ferric ion is the indicator. The deep red ferric thiocyanate color appears only when the silver is completely titrated. Gravimettically, silver is determined by precipitation with chloride, sulfide, or 1,2,3-benzotriazole. Silver can be precipitated as the metal by electrodeposition or chemical reducing agents. A colored silver diethyldithiocarbamate complex, extractable by organic solvents, is used for the spectrophotometric determination of silver complexes. 

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