Water, thioacetamide precipitation

A Thioacetamide-Precipitation Procedure for Determining Trace Elements in Water... 

Three water samples which had previously been analyzed by several other spectrographic laboratories were analyzed by the thioacetamide precipitation method described here. Although there is a considerable range of reported concentrations, as might be expected for such analyses, the results of the thioacetamide-spectrochemical method generally were comparable with those reported by others (Table VI). 

In the titration of thioacetamide with silver nitrate in distilled water and in slightly acidic or basic solution, a black precipitate of silver sulfide formed. The other products of the reaction were ammonium nitrate and acetic acid. Two reaction pathways have been suggested for the course of this reaction, Scheme 3 and equation (24).349,330 In the presence of 0.1 MHN03, the reaction proceeded similarly. However, in 0.5 M or more concentrated HN03 solutions a different reaction took place. Under these conditions a light, pearly precipitate was formed and a silver thioacetamide complex was obtained. 

Acidic (pH 2-4.5, adjusted by acid) aqueous mixtures containing a Cd salt such as CdCl2 and thioacetamide (TAA), which decomposes more easily than TU in acidic solutions, are used as the bath. When the mixture is heated to around 70°C in a water bath, yellow turbidity develops in solution because of precipitation of CdS according to the reaction,... 

Wear nitrile rubber gloves, eye protection, and laboratory coat. Avoid breathing dust. In the fume hood, dissolve the arsenic compound in acidified boiling water (for 1 g of arsenic compound, use 100 mL of water containing 6 drops of concentrated hydrochloric acid). Add a solution of thioacetamide (for each 1 g of arsenic salt, use 0.2 g of thioacetamide in 20 mL of water). Boil the mixture for 20 minutes and then basify with 2 M sodium hydroxide (prepared by dissolving 8 g of NaOH in 100 mL of water). Filter the precipitate, dry, and package for disposal in a secure landfill site. ... 

Catalyst with 12% Mo loading was deposited on silica support via precipitation of metal sulphide from a homogenous solution containing calculated amount of ammonium molybdate ((NH4)Mo7024.4H20), urea, thioacetamide and nitric acid. Reaction was carried out in a water bath shaker kept at 90 C for 3 hours. The slurry was then filtered and the precipitate was dried in oven at 120 C for 14 hours. All chemicals were obtained from Aldrich as AnalaR grade and ultra-pure water was used to prepare the solutions... 

Thioacetamide has been used as a substitute for hydrogen sulfide. It is readily obtainable, and the commercial product tested was free of all heavy-metal sulfides except a trace of silver. Thioacetamide is very soluble in alcohol, benzene, or water. The neutral water solution is stable for long periods of time. A slight cloudiness may form in long-stored water solutions but this may be removed by filtration. A solution of thioacetamide can be added directly to solutions so there is no loss of precipitate in hydrogen sulfide delivery tubes. 

Wash solution I (acid precipitation). Dissolve 80 mg. of thioacetamide in 1 liter of demineralized water. Adjust the pH to 0.75 with 3N HQ. 

An aqueous solution of 100ml containing 10ml of cobalt nitrate (0.1ml), 5g urea, 1ml nitric acid (0.75N) and 30ml of thioacetamide solution (0.133M) placed in a 250ml conical flask. The flask was covered with rubber cork and the contents in the flask were heated on a water bath (90-95°C) for about 2j hours by intermittent stirring. After the precipitation was complete pH (7.5 to 8.5), it was filtered, washed with distilled water and dried at 110°C for 1 hour. 

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