Silver thiosulphate

Silver nitrate solution white precipitate of silver thiosulphate ... 

On warming with water, silver thiosulphate decomposes, precipitating silver sulphide and forming sulphuric acid ... 

With silver halides sodium thiosulphate forms a soluble sodium silver thiosulphate, and is employed as a fixing material for photographic plates and paper to remove the portion of silver salt unaffected by light ... 

Simmons, W., Gonnissen, D., and Hubin, A. 1997. Study of the initial stages of silver electrocrystallisation from silver thiosulphate complexes Part I. Modelling of the silver nuclei formation during the induction period. Journal of Electroanalytical Chemistry 433, 141-151. 

Again, when silver thiosulphate is warmed srith water, black sulphide of silver separates ou and the solution oontaius free... 

Silver chloride is readily soluble in ammonia, the bromide less readily and the iodide only slightly, forming the complex cation [Ag(NH3)2]. These halides also dissolve in potassium cyanide, forming the linear complex anion [AglCN) ] and in sodium thiosulphate forming another complex anion, [Ag(S203)2] ... 

It was known in the sixteenth century that silver salts were photosensitive, but it was not until the beginning of the nineteenth century, when Herschel found that silver chloride was soluble in sodium thiosulphate, that photography became possible. 

I he methyl iodide is transferred quantitatively (by means of a stream of a carrier gas such as carbon dioxide) to an absorption vessel where it either reacts with alcoholic silver nitrate solution and is finally estimated gravimetrically as Agl, or it is absorbed in an acetic acid solution containing bromine. In the latter case, iodine monobromide is first formed, further oxidation yielding iodic acid, which on subsequent treatment with acid KI solution liberates iodine which is finally estimated with thiosulphate (c/. p. 501). The advantage of this latter method is that six times the original quantity of iodine is finally liberated. 

In order to prepare an acid, a dioxan solution of the diazo ketone is added slowly to a suspension of silver oxide in a dilute solution of sodium thiosulphate Iftheco)iversion to the acid yields unsatisfactory results, it is usually advisable to prepare the ester or amide, which are generally obtained in good yields hydrolysis of the derivative gives the free acid. 

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°. 

Add, with stirring, a solution of 6 8 g. of the fiis-diazo ketone in 100 ml. of warm dioxan to a suspension of 7 0 g. of freshly precipitated silver oxide in 250 ml. of water containing 11 g. of sodium thiosulphate at 75°. A brisk evolution of nitrogen occurs after 1 5 hours at 75°, filter the liquid from the black silver residue. Acidify the almost colourless filtrate with nitric acid and extract the gelatinous precipitate with ether. Evaporate the dried ethereal extract the residue of crude decane-1 10-dicarboxylic acid weighs 4 -5 g. and melts at 116-117°. RecrystaUisation from 20 per cent, aqueous acetic acid raises the m.p. to 127-128°. 

Discussion. Silver can be extracted from a nearly neutral aqueous solution into nitrobenzene as a blue ternary ion association complex formed between silver(I) ions, 1,10-phenanthroline and bromopyrogallol red. The method is highly selective in the presence of EDTA, bromide and mercury(II) ions as masking agents and only thiosulphate appears to interfere.8... 

Determination of silver as chloride Discussion. The theory of the process is given under Chloride (Section 11.57). Lead, copper(I), palladium)II), mercury)I), and thallium)I) ions interfere, as do cyanides and thiosulphates. If a mercury(I) [or copper(I) or thallium(I)] salt is present, it must be oxidised with concentrated nitric acid before the precipitation of silver this process also destroys cyanides and thiosulphates. If lead is present, the solution must be diluted so that it contains not more than 0.25 g of the substance in 200 mL, and the hydrochloric acid must be added very slowly. Compounds of bismuth and antimony that hydrolyse in the dilute acid medium used for the complete precipitation of silver must be absent. For possible errors in the weight of silver chloride due to the action of light, see Section 11.57. 

Thiosulphate as Ag2S. Add a slight excess of 0.1 M silver nitrate solution to the cold, almost neutral, thiosulphate solution. Heat at 60 °C in a covered vessel and, after cooling, filter and wash the silver sulphide precipitate with ammonium nitrate solution, water and finally with ethanol. Dry at 110°C and weigh as Ag2S (Section 11.76). 

Chlorate, D. of as silver chloride, (g) 479 by potassium dichromate, (ti) 378 by sodium thiosulphate, (ti) 394 Chloride and bromide, separation of on an anion exchanger, 209... 

Linear S-Au-S (but non-linear Au-S-C) is found in PhAs+Au(SCN)2 [96] related phosphine complexes (R3P) AuSCN have been made (section 4.10.3). Sulphate and thiosulphate bind through sulphur Na3Au(S203)2.2H20 has linear 2-coordinate gold in contrast to tetrahedral coordination of silver by sulphur and oxygen. 

Fortin, C. and Campbell, P. G. C. (2001). Thiosulphate enhances silver uptake by a green alga role of anion tranporters in metal uptake, Environ. Sci. Technol., 35, 2214-2218. 

Industrially, the silver is recovered from either the wash water, or the bleach fix separately or from a mixture of the two using electrolysis employing a stainless steel cathode cylinder and an anode of stainless steel mesh. A typical wash solution composition contains silver (4 g L ), sodium thiosulphate (220 g L ), sodium bisulphite (22 g L ) and sodium ferric EDTA (4 g L ). At Coventry we have used a scaled down version of the industrial process employing 250 mL samples [46]. Electrolysis experiments were performed at ambient temperature with both wash and bleach fix solutions and in which the potential applied to the cathode and the speed of rotation of the cathode were varied. The sonic energy (30 W) was supplied by a 38 kHz bath. The results are given in Tab. 6.9. The table shows that the recovery of silver on sonication of the wash or bleach fix solutions is much improved especially if the electrode is rotated while ultrasound is applied. Yields with bleach fix (which contains ferric ions) are less since Fe and Ag compete for discharge (Eqs. 6.13 and 6.14). 

One possible reaction which hinders the total removal of the silver is the formation of a complex between silver and thiosulphate ions (Eq. 6.15). Whilst the removal of such a large quantity of sodium thiosulphate (220 g L- prior to discharge of silver is not economically feasible, removal (discharge) of thiosulphate is improved in the presence of ultrasound (Tab. 6.10). 

Silver M, Kelly DP. 1976a. Rhodanese from Thiobacillus A2 catalysis of reactions of thiosulphate with dihydrolipoate and dihydrolipoamide. J Gen Microbiol 97 277-84. 

To date, only the second form of ternary adsorption has been observed for iron oxides. Davis and Leckie (1978 a) found that thiosulphate adsorbed on ferrihydrite in acid media with adsorption decreasing to zero as the pH rose to ca. 7, whereas the adsorption edge of silver lay between pH 7 and 8. In the presence of thiosulphate, adsorption of silver was enhanced in the pH range 4-6.5 (Fig. 10.10), i. e. 

---