Sodium thiosulfate solutions titration

Effluent-gas Analysis.4 This method of analysis gives an estimate both of the chlorine (IV) oxide produced and of the unreacted chlorine present in the effluent-gas mixture. The gas is collected in an opaque 600-ml. Hempel tube it is then absorbed in a neutral 10% solution of potassium iodide. Starch indicator is added to this solution or to an aliquot, which is then titrated with 0.1 AT sodium thiosulfate solution (titration A). The amount of sodium thiosulfate used is equivalent to all the chlorine gas in the sample plus one-fifth of the chlorine(IV) oxide. The solution is then acidified with an excess of 30% acetic acid, causing a second release of iodine, which is then titrated with sodium thiosulfate solution (titration B). The amount of sodium thiosulfate used in titration B is equivalent to four-fifths of the chlorine (IV) oxide in the sample. The equations for the reactions involved are shown below.4... 

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 is titrated with standard sodium thiosulfate solution. In the thiosulfate method, selenous acid is treated with an excess of standard sodium thiosulfate solution ... 

The benzoylperoxide used was analyzed by dissolving r g. in 25 cc. of dry ether and adding 2 cc. of 5 per cent sodium ethylate solution, keeping the temperature below — 50. The ether solution was extracted with exactly 100 cc. of cold water and an aliquot part of the aqueous extract taken. To this was added 2 cc. of 5 per cent potassium iodide and 2 cc. of dilute hydrochloric acid and the liberated iodine was titrated with 0.1 N sodium thiosulfate solution. The peroxide analyzed 90 per cent pure. 

Absorb in an impinger containing a standardized solution of iodine and potassium iodide titrate with standard sodium thiosulfate solution. Iodometric titration No data NR EPA 1978... 

Soliman and Belal investigated argentimetric (67,68) and mercurimetric (69) methods. Hydralazine precipitates silver from ammoniacal silver nitrate solution. The silver is dissolved with hot nitric acid and titrated with ammonium thiocyanate solution. Alternatively, mercury is precipitated from alkaline potassium mercuric iodide solution. The precipitated mercury is dissolved by adding excess standard iodine solution. The excess iodine is back-titrated with sodium thiosulfate solution after acidifying with acetic acid. 

Add most of the HC1 required immediately and complete the titration in not more than 1 minute. Make a blank determination with the same quantity of sodium thiosulfate solution. Calculate the percentage of Hg fulminate as follows ... 

The combined filtrates may be titrated with 1 N sodium thiosulfate solution to determine the yield of monochlorourea. This preparation of monochlorourea is a modification of procedures previously described> ... 

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 ... 

Iodometric titration was carried out as shown below About 100 mg. of hydroxylamine-O-sulfonic acid was exactly weighed and dissolved in 20 ml. of distilled water. Sulfuric acid (10 ml. of 10% solution) and 1 ml. of saturated potassium iodide solution were then added. After the solution was allowed to stand for 1 hour, liberated iodine was titrated with 0.1 N sodium thiosulfate solution until the iodine color disappeared. The following stoichiometric relation was used 0.1 N Na2S203 (1 ml.) = 5.66 mg. H3NOSO3. Hydroxylamine-O-sulfonic acid should be stored in tightly sealed bottles in a refrigerator. 

The peroxy group is detemiined by treatment with sodium iodide. The liberated iodine is then titrated with standard sodium thiosulfate solution. The reaction is... 

The water forces thefat/oil into the cyclohexane and the excess iodine monochloride moves into the water, where it is converted to I2 and can be titrated with the water-soluble sodium thiosulfate. Potassium iodide solution acts to convert the excess iodine monochloride to free iodine (blue) which can be titrated to a colorless end point with sodium thiosulfate. Soluble starch aids in being able to see the free iodine and getting a repeatable end point. The normality of the sodium thiosulfate solution used is generally ft 1N however, this may change depending on the level of iodine monochloride that is to be titrated. Ideally any titration should use between 5 and 50 ml (1 buret volume) of solution—titrations outside of this range can produce unreliable data. 

The determination of peroxide value (PV) by an iodometric titration is described in Basic Protocol 2. Iodine is liberated by hydroperoxides in the oil in the presence of excess iodide in a stoichiometric ratio. The amount of iodine present is determined by titration with a standard sodium thiosulfate solution using a starch indicator, thereby reflecting how much peroxide is present in the oil or lipid extract. 

If the expected peroxide content in the sample is low, a standardized -0.05 N or 0.01 N sodium thiosulfate solution should be used for the titration. 

Continue titration, shaking flask vigorously near the endpoint to liberate all iodine from the chloroform layer. Add sodium thiosulfate solution dropwise until the violet color disappears. Record the total added sodium thiosulfate volume. 

The blank titration must not exceed 0.1 ml sodium thiosulfate solution. If a 0.1-ml volume is exceeded, fresh reagents should be prepared and the new thiosulfate solution standardized. If the problem persists, the purity of the chemicals employed should be examined. 

A 2-ml. aliquot of the solution, withdrawn by means of a safety pipet, is added to 20 ml. of water containing 2 g. of potassium iodide, and the liberated iodine is titrated with good shaking with standard sodium thiosulfate solution. 

The excess iodine (unreacted surplus iodine) is back titrated with standard sodium thiosulfate solution using starch indicator. Phenylarsine oxide may be used as a titrant instead of sodium thiosulfate. 

Difluoromethoxy-2-[(4,5-dimethoxy-2-pyridyl)methylthio]-lH-benzimidazole (about 1 g) are dissolved in 10 ml of dioxane and 2 ml of 1 N sodium hydroxide solution. An equimolar amount of a titrated aqueous sodium hypochlorite solution, to which 1 mole per liter of sodium hydroxide solution has been added, is first added dropwise, while cooling with ice. After one hour a further equivalent and after 3 hours half the equimolar amount of sodium hypochlorite are added, to achieve complete reaction. After a reaction time of 4 hours, 5 ml of 5% strength sodium thiosulfate solution and another 25 ml of dioxane are added and the upper dioxane phase is separated off, washed once with 5 ml of sodium thiosulfate solution and concentrated on a rotary evaporator. The oily residue is dissolved in 20 ml of water and 10 ml of ethyl acetate and the solution is brought to pH 7 with about 100 ml of a buffer solution of pH 6.8. The solid which has precipitated out is filtered off with suction over a suction filter, washed with water, extracted by stirring at OC with acetone and dried. 5-Difluoromethoxy-2-[(4,5-dimethoxy-2-pyridyl)methanesulfinyl]-lH-benzimidazole is prepared yield about 85%. 

Sodium Chlorite. An accurately weighed sample of about 2.0 g. of sodium chlorite is dissolved in 1 1. of water a 25-ml. aliquot serves as the sample for analysis. Two milliliters of 50 % potassium iodide and 10 ml. of acetic acid are added to the aliquot, and the ensuing reaction is allowed to proceed in the dark for 5 minutes. The liberated iodine is then titrated with 0.1 A standard sodium thiosulfate solution, using starch as an indicator. The equations for the reactions are written below.1... 

Determination of the Hydroperoxide. Glacial acetic acid (30 ml.) containing 0.0005% ferric chloride hexahydrate and 5 ml. saturated potassium iodide solution was added to an aliquot of the hydroperoxide solution which had been flushed with nitrogen. The mixture was stored in the dark for 10 minutes, diluted with water (50 ml.), and the liberated iodine was titrated with sodium thiosulfate solution using starch as indicator. 

Ozone Production Rate. The ozone rate was determined by passing the gas stream from the ozone generator into an aqueous 10% potassium iodide solution and titrating the iodine that was liberated with standard sodium thiosulfate solution. 

The purity is determined by titration with standard sodium thiosulfate solution. An accurately weighed sample of about 200 mg. is dissolved in water, and a solution of approximately 1 g. of potassium iodide in 10 ml. of water is added. The solution is acidified with 10 ml. of 10% sulfuric acid and titrated with 0.1 A thiosulfate to the starch end point. 

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