Copper with sodium thiosulfate

Synthesis. The method of synthesis for Methylene Blue described in reference 14 is stiU the stepwise method of choice for thiazine dyes. /V,/V-Dimethy1-y-pheny1ene diamine [99-98-9], CgH22N2, reacts with sodium thiosulfate [7772-98-7] to form the thiosulfonic acid which condenses with /V, /V-dimetby1 ani1 ine [121 -69-7], CgH N, in the presence of sodium dichromate [10588-01-9] to the indamine, then with copper sulfate [18939-61 -2] and sodium dichromate to Methylene Blue (26). 

Although silver is not treated by solvent extraction in any of the flow sheets, silver is recovered from aqueous solution in several other situations. For these processes, Cytec developed reagents with donor sulfur atoms to extract this soft element. For example, tri-isobutylphosphine sulfide (CYANEX 47IX) extracts silver from chloride, nitrate, or sulfate media selectively from copper, lead, and zinc [32]. The silver is recovered from the loaded organic phase by stripping with sodium thiosulfate, and the metal recovered by cementation or electrolysis. Silver can also be extracted from chloride solution by a dithiophosphinic acid (CYANEX 301) [33]. 

As an illustration of the use of electrode potentials, consider the classical method of analysis of copper in brass, which involves dissolving the weighed sample in nitric acid to obtain Cu2+(aq), adjusting the pH to a weakly acidic level, allowing the Cu2+ to react completely with excess potassium iodide to form iodine and the poorly soluble Cul, and then titrating the iodine with sodium thiosulfate solution that has been standardized against pure copper by the same procedure ... 

Bronze is an alloy of copper and tin. A 0.6554-g sample of a certain bronze was reacted with nitric acid and the tin removed. After appropriate treatment of the solution, titration with sodium thiosulfate revealed that it contained 8.351 millimoles of copper. Calculate the percentages of copper and tin in this bronze. 

CUCI2 has been studied spectroscopically at 1000 °C in the presence of CI2 (to prevent decomposition to CuCl and Cb). Binary copper compounds with very soft iodide ligands are not known by simply adding 1 to a solution of Cu +, Cul and I2 are quickly formed. This reaction can be used for the volumetric analysis of Cu + in solution by titrating the I2 produced with sodium thiosulfate (equation 8). Hydrates of the dihalides (F, Cl, Br) are common, easily prepared from aqueous haloacids, and contain coordinated water molecules. 

This reaction occurs because of the extraordinary stability of cuprous iodide, which is discussed in the following section. The reaction is used in a method of quantitative analysis for copper, the liberated iodine being determined by titration with sodium thiosulfate solution. 

Consider the analysis of copper in brass (a mixture of copper and zinc) by dissolving brass in concentrated nitric acid followed by the addition of excess iodide ions. Iodine is produced in an amount equivalent to that of the oxidizing agent (Cu ) present in the sample. The liberated iodine is then titrated with sodium thiosulfate. 

Corrosion. Copper-base alloys are seriously corroded by sodium thiosulfate (22) and ammonium thiosulfate [7783-18-8] (23). Corrosion rates exceed 10 kg/(m yr) at 100°C. High siUcon cast iron has reasonable corrosion resistance to thiosulfates, with a corrosion rate <4.4 kg/(m yr)) at 100°C. The preferred material of constmction for pumps, piping, reactors, and storage tanks is austenitic stainless steels such as 304, 316, or Alloy 20. The corrosion rate for stainless steels is <440 g/(m yr) at 100°C (see also Corrosion and corrosion control). 

Determination. The most accurate (68) method for the deterrnination of copper in its compounds is by electrogravimetry from a sulfuric and nitric acid solution (45). Pure copper compounds can be readily titrated using ethylene diamine tetracetic acid (EDTA) to a SNAZOXS or Murexide endpoint. lodometric titration using sodium thiosulfate to a starch—iodide endpoint is one of the most common methods used industrially. This latter titration is quicker than electrolysis, almost as accurate, and much more tolerant of impurities than is the titration with EDTA. Gravimetry as the thiocyanate has also been used (68). 

Twenty-five grams (0.1 mol) of copper(II) sulfate 5-hydrate is placed in a 400-ml. beaker and dissolved in 150 ml. of water. A second solution is prepared by placing 36.5 g. (0.22 mol) of potassium iodide and 28.0 g. (slightly more than 0.11 mol) of sodium thiosulfate 5-hydrate in a 100-ml. volumetric flask, adding water to the mark, and shaking thoroughly, f The second solution is added to the first from a buret with continuous, rapid stirring until no further precipitation occurs (90.9 ml. is theoretically required). J... 

Copper (I) iodide is a dense, pure white solid, crystallizing with a zinc-blende structure below 300°. It is less sensitive to light than either the chloride or bromide, although passage of air over the solid at room temperature in daylight for 3 hours results in the liberation of a small amount of iodine. It melts at 588°, boils at 1,293°, and unlike the other copper halides, is not associated in the vapor state. Being extremely insoluble (0.00042 g./l. at 25°), it is not perceptibly decomposed by water. It is insoluble in dilute acids, but dissolves in aqueous solutions of ammonia, potassium iodide, potassium cyanide, and sodium thiosulfate. It is decomposed by concentrated sulfuric and nitric acids. 

Repeat the entire procedure with the dextrose standard (5 mL of Dextrose Standard Solution and 5 mL of Copper Reagent Solution), noting the volume of 0.005 N sodium thiosulfate consumed as Vj> Run a corresponding blank titration, Vb> using 5 mL of water and 5 mL of Copper Reagent Solution. 

Cellulose can be modified with organostannane chlorides, such as dibutyl or triphenyl derivatives [91,92], or with organotin halides in the presence of bisethylenediamine copper(II) hydroxide [93]. Epoxy-activated cellulose was prepared by reacting cellulose acetate fibers with sodium methoxide, followed by reacting it with epichlorohydrin in DMSO. This epoxy-activated cellulose has proved to be a useful intermediate to react with substances containing active hydrogen, such as amine, amino acid, or carboxylic acids [94], as shown in Fig. 3. Epoxidized cellulose has also been converted to a thiol derivative via reduction of a thiosulfate intermediate [95], and sulfoethylcellu-[ose has been obtained from sodium chloroethanesulfonate [96]. Cellulose... 

A definite method for the determination of D-fructose in the presence of aldoses was worked out by Kruisheer 98.3% of theory was found. The aldoses were oxidized with sodium hypoiodite, after which the excess iodine was titrated with sodium sulfite. Thiosulfate could not be used here, since the subsequent determination of D-fructose was carried out with an alkaline copper solution by the Luff-Schoorl method. 

Benzoyl disulfide has been obtained by the reaction of benzoyl chloride with hydrogen sulfide, hydrogen disulfide, hydrogen trisulfide, potassium sulfide, sodium disulfide, lead sulfide, sodium hydrosulfite, sodium thiosulfate, sulfhydrylmagnesium bromide, and thiobenzamide. It is also formed by reaction of benzoic anhydride with hydrogen sulfide. The better preparative methods involve the oxidation of thiobenzoic add by means of air,hydrogen peroxide or sulfur monochloride, or of the sodium or potassium salt by means of air, - chlorine, iodine, copper sulfate, - potassium ferricyanide, - or ferric chloride. - ... 

Other primary standards for sodium thiosulfate are potassium dichromate, potassium bromate, potassium hydrogen iodate, potassium hexacyanoferrate(III), and metallic copper. All these compounds liberate stoichiometric amounts of iodine when treated with excess potassium iodide. 

ESther commercially available copper(I) iodide or that obtained by reduction of a copper (II) salt solution with a soluble iodide in the presence of sodium thiosulfate to remove liberated iodine can be employed. 

Employees should be informed of the risks of exposure to corrosive agents and be well trained to handle the chemicals as well as to act when they have been exposed. Showers for rapid irrigation with water should be easily accessible. A 1% copper sulfate solution, polyethylene glycol 300 or 400, 5% sodium thiosulfate solution, and a proper calcium preparation should be present in the first-aid kit. A calcium preparation for topical treatment should also be present near any employees work site where hydrofluoric acid or fluorides are used. Workers at risk should wear proper protective equipment, which may include eye glasses, face masks, gloves, boots, and safety dresses. 

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