Thiosulfates analysis

Chlorine and bromine add vigorously, giving, with proper control, high yields of 1,2-dihaloethyl ethers (224). In the presence of an alcohol, halogens add as hypohaUtes, which give 2-haloacetals (225,226). With methanol and iodine this is used as a method of quantitative analysis, titrating unconsumed iodine with standard thiosulfate solution (227). 

An alternative method for the analysis of permanganate is the use of conventional iodometric methods (177) where excess potassium iodide is added to a solution of permanganate under acidic conditions. The Hberated iodide is then titrated with standard thiosulfate solution using starch as an indicator. 

The hberated iodine is measured spectrometricaHy or titrated with Standard sodium thiosulfate solution (I2 +28203 — 2 1 VS Og following acidification with sulfuric acid buffers are sometimes employed. The method requires measurement of the total gas volume used in the procedure. The presence of other oxidants, such as H2O2 and NO, can interfere with the analysis. The analysis is also technique-sensitive, since it can be affected by a number of variables, including temperature, time, pH, iodide concentration, sampling techniques, etc (140). A detailed procedure is given in Reference 141. 

The hberated iodine, as the complex triiodide ion, may be titrated with standard thiosulfate solution. A general iodometric assay method for organic peroxides has been pubUshed (253). Some peroxyesters may be determined by ferric ion-catalyzed iodometric analysis or by cupric ion catalysis. The latter has become an ASTM Standard procedure (254). Other reducing agents are ferrous, titanous, chromous, staimous, and arsenite ions triphenylphosphine diphenyl sulfide and triphenjiarsine (255,256). 

A double end point, acid—base titration can be used to determine both sodium hydrosulfide and sodium sulfide content. Standardized hydrochloric acid is the titrant thymolphthalein and bromophenol blue are the indicators. Other bases having ionization constants in the ranges of the indicators used interfere with the analysis. Sodium thiosulfate and sodium thiocarbonate interfere quantitatively with the accuracy of the results. Detailed procedures to analyze sodium sulfide, sodium hydro sulfide, and sodium tetrasulfide are available (1). 

Ana.lytica.1 Methods. Various analytical methods involve titration with oxidants, eg, hexacyanoferrate (ferricyanide), which oxidize dithionites to sulfite. lodimetric titration to sulfate in the presence of formaldehyde enables dithionite to be distinguished from sulfite because aldehyde adducts of sulfite are not oxidized by iodine. Reductive bleaching of dyes can be used to determine dithionite, the extent of reduction being deterrnined photometrically. Methods for determining mixtures of dithionite, sulfite, and thiosulfates have been reviewed (365). Analysis of dithionite particularly for thiosulfate, a frequent and undesirable impurity, can be done easily by Hquid chromatography (366). 

X-ray crystallographic analysis of the sodium thiosulfate pentahydrate [10102-17-7] crystal indicates a tetrahedral stmcture for the thiosulfate ion. The S—S bond distance is 197 pm the S—O bond distance is 148 pm (5). Neutron diffraction of a barium thiosulfate monohydrate [7787-40-8] crystal confirms the tetrahedral stmcture and bond distances for the thiosulfate ion (6). 

Analytical and Test Methods. Analysis and test methods are similar to those for sodium thiosulfate. Sulfite is determined by an indirect method based on the titration of the acid Hberated when both the sulfite and thiosulfate are oxidized with iodine solution (69). 

Peracid Analysis. Peracid concentrations can be measured in a product or in the bath by use of a standard iodide / thiosulfate titration (60). With preformed peracids or peracids formed via perhydrolysis care must be exercised to minimize the interference of hydrogen peroxide, present intentionally as a component of the perhydrolysis reaction or as a result of the hydrolysis of the peracid (87,88) as shown in equation 18. 

Use of a pH buffer of 8—9 has been suggested as a substitute for the pH 7 buffer for more accurate analysis. Sodium thiosulfate [10102-17-7] Na2S202, or phenylarsine oxide [637-03-6] C H AsO, are the typical titrants. 

Assay of hydrogen cyanide can be done by specific gravity or silver nitrate titration. Sulfur dioxide in hydrogen cyanide can be deterrnined by infrared analysis or by reaction of excess standard iodine solution and titration, using standard sodium thiosulfate or by measurement of total acidity by... 

Examples of such irreversible species (12) include hydroxjiamine, hydroxide, and perchlorate. The electrochemistries of dichromate and thiosulfate are also irreversible. The presence of any of these agents may compromise an analysis by generating currents in excess of the analytically usehil values. This problem can be avoided if the chemical reaction is slow enough, or if the electrode can be rotated fast enough so that the reaction does not occur within the Nemst diffusion layer and therefore does not influence the current. 

The former reaction, in particular, affords a convenient means of quantitative analysis by determination of the H2S (precipitated as CdS) and iodometric determination of the thiosulfate produced. 

The amount of sodium hypochlorite in a bleach solution can be determined by using a given volume of bleach to oxidize excess iodide ion to iodine CIO- is reduced to Cl-. The amount of iodine produced by the redox reaction is determined by titration with sodium thiosulfate, Na2S203 I2 is reduced to I-. The sodium thiosulfate is oxidized to sodium tetrathionate, Na2S406. In this analysis, potassium iodide was added in excess to 5.00 ml of bleach d = 1.00 g/cm3). If 25.00 mL of 0.0700 MNa2S203 was required to reduce all the iodine produced by the bleach back to iodide, what is the mass percent of NaCIO in the bleach ... 

The liberated iodine may be titrated using std thiosulfate soln, or, in trace analysis, detd by spectrophotometric methods. Other reducing agents commonly used in peroxide analysis are hydriodic acid, ferrous, titanous, stannous, and arsenious ions. Also (recently), triphenylphos-phine, which is oxidized to triphenyl phosphine oxide. The excess triphenyl phosphine may be detd gravimetric ally, tit rime trically, or spectro-photometrically... 

Tests. Chem analysis consists of reaction with KI soln and titration of the liberated I with Na thiosulfate soln. Instrumental analysis consists of measurement of the carbonyl absorption at 1760cm 1 using an infrared spectrophotometer. This procedure is valid for any physical state or soln strength of the acid (Ref 10)... 

Recendy, ID quantum dots of gallium selenide with average diameter 8-10 nm, connected in the form of chains of average length 50-60 nm, were synthesized on rro substrates by cathodic electrodeposition from acidic aqueous solutions of gallium(III) nitrate and selenious acid [186], The structural analysis from XRD patterns revealed the formation of Ga2Se3/GaSe composition. The films were found to be photoactive in aqueous sodium thiosulfate solution and showed p-type conductivity. 

Figure 10 Capillary ion analysis of 30 anions 1 = thiosulfate, 2 = bromide, 3 = chloride, 4 = sulfate, 5 = nitrite, 6 = nitrate, 7 = molybdate, 8 = azide, 9 = tungstate, 10 = monofluorophosphate, 11 = chlorate, 12 = citrate, 13 = fluoride, 14 = formate, 15 = phosphate, 16 = phosphite, 17 = chlorite, 18 = galactarate, 19 = carbonate, 20 = acetate, 21 = ethanesulphonate, 22 = propionate, 23 = propanesulphonate, 24 = butyrate, 25 = butanesulphonate, 26 = valerate, 27 = benzoate, 28 = D-glutamate, 29 = pentane-sulphonate and 30 = D-gluconate. Experimental conditions fused silica capillary, 60 cm (Ld 52 cm) x 50 p i.d., voltage 30 kV, indirect UV detection at 254 nm, 5 mM chromate, 0.5 mM NICE-Pak OFM Anion-BT, adjusted to pH 8.0, with 100 mM NaOH. (From Jones, W. R. and Jandik, R, /. Chromatogr., 546, 445,1991. With permission.)...

Sodium thiosulfate, 23 674 use in selenium analysis, 22 94-95 Sodium titanate, 25 100 Sodium toluenesulfonate... 

Preparative Photolysis. The preparative photolysis of an aqueous solution (pH=8.5) of AETSAPPE (2.5 M) was conducted in a 1-inch diameter quartz test tube in a Rayonet Reactor (Southern New England Radiation Co.) fitted with 254 nm lamps. Within two hours the solution gelled and the reaction was terminated. Upon acidification the solution cleared, and the product could be re-precipitated by addition of base. This indicates loss of the thiosulfate functionality. The product was dissolved in dilute HC1, precipitated with acetone, and filtered. This process was repeated three times, and the final precipitate was washed with water. The product (20 to 30 mg) was dried in vacuo for 24 hours and stored in a dessicator until use. Comparison of the13 C NMR spectrum of the product with the starting AETSAPPE 13C NMR spectrum clearly shows that the thiosulfate methylene peak shifted upfield, from 39 ppm to 35 ppm. The complete 13 C NMR and IR analysis of the product were consistent with the disulfide product. Further, elemental analysis of the product confirmed that the product was the desired disulfide product 2-amino (2-hydroxy 3-(phenyl ether) propyl) ethyl disulfide (AHPEPED) Expected C 58.39, H 7.08, N 6.20, S 14.18 actual C 58.26, H 7.22, N 6.06, S 14.28. 

In addition, from the analysis of the ac impedance spectra obtained from the previously pitted surfaces under open circuit conditions at room temperature in 0.5 M Na2S04 solution51 and from the in-situ pitted surfaces in Cl ion-containing thiosulfate solution at various applied potentials and solution temperatures,52 they verified that dr>ss is inversely proportional to the CPE exponent for capacitive charging process (Eq. 30)51 and the depression parameter for charge transfer process.52... 

Sylvester DM, Holmes RK, Sander C, et al. 1982. Interference of thiosulfate with potentiometric analysis of cyanide in blood and its elimination. Toxicol Appl Pharmacol 65 116-121. 

The formation of S-alkyl thiosulfate (Bunte salt) by the reaction of alkyl halide and sodium thiosulfate has been well known. Whereas a patent claimed the formation of Bunte salt from PECH and sodium thiosulfate (23), the reaction hardly proceeded in DMF owing to low solubility of sodium salt. On the other hand, both ammonium thiosulfate and PECH were soluble in HMPA-H20 (7 1 vol/vol) and the reaction proceeded homogeneously. Water soluble Bunte salt (j2, v(S0), 1200, 1020 cm-1) was isolated by pouring the reaction mixture into water and salting out with ammonium chloride. The DS based on the mercuric nitrate titration was in nearly accord with that on elemental analysis. The DS values depended on the thiosulfate concentration were shown below. 

Analysis of this substance, just prior to use, is carried out in the following manner. A sample is dissolved in water and treated with a solution of potassium iodide in 2N sulfuric acid. After 5 minutes the solution is titrated with thiosulfate solution near the end of the titration the solution is boiled to ensure completeness of iodine liberation. Instead of the 90% product, a correspondingly greater amount of the 80% product can be employed. 

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