Sodium thiosulfate solution, volumetric

Sodium Thiosulfate Solution (0.100 N) Dissolve 24.820 g of sodium thiosulfate in approximately 75 25 mL of freshly boiled water, and add 0.10 0.01 g of sodium carbonate. Quantitatively transfer the mixture to a 1-L volumetric flask, and dilute to volume with water. Allow the solution to stand for a minimum of 4 days before standardizing. Store the solution in an amber bottle. 

Standardized Sodium Thiosulfate Solution Dissolve about 8.7 g of sodium thiosulfate (Na2S203-5H20) and 67 mg of sodium carbonate in 1000 mL of freshly boiled and cooled water. Add 3 mL of 1.0 N sodium hydroxide. This solution contains 5.54 g of sodium thiosulfate. Standardize to 0.0333 N as directed for 0.1 N Sodium Thiosulfate (see Volumetric Solutions under Solutions and Indicators). Adjust the normality repeatedly, if necessary. 

Sodium Thiosulfate TS Use 0.1 N Sodium Thiosulfate (see Volumetric Solutions in this section). 

According to Hllllbrand and Lundell (H3) the best of the volumetric methods for lead Is precipitation of lead chromate from acetic acid solution, dissolution of the washed precipitate In hydrochloric acid, addition of excess potassium Iodide and titration of the liberated Iodine with a standard sodium thiosulfate solution. This procedure has recently been reviewed by Ryazanov (R2). 

Q7 A 0.6125 g sample of potassium iodate(v), KIO3, is dissolved in distilled water and made up to 250.00cm in a volumetric flask. A 25.00cm portion of the solution is added to an excess of acidified potassium iodide solution. The iodine formed requires 24.50cm of sodium thiosulfate solution for titration. 

The sample is acidified with sulfuric acid. The bromide content is then determined by the volumetric procedure described by Kolthoff and Yutzy [21 ]. In this procedure the buffered sample is treated with excess sodium hypochlorite to oxidise bromide to bromate. Excess hypochlorite is then destroyed by addition of sodium formate. Acidification of the test solution with sulfuric acid followed by addition of excess potassium iodide liberates an amount of iodine equivalent to the bromate (i.e., the original bromide) content of the sample. The liberated iodine is titrated with standard sodium thiosulfate. 

These solutions can be prepared by accurately pipetting 500 ml or 100 ml of 0.1 N sodium thiosulfate, respectively, into a 1000-ml volumetric flask and then accurately diluting to volume with recently boiled distilled water. 

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... 

Assay Transfer about 120 mg of sample, previously dried at 105° for 1 h and accurately weighed, into a 100-mL volumetric flask, dissolve in and dilute to volume with water. Transfer 50.0 mL of this solution into a 250-mL glass-stoppered iodine flask, add 50.0 mL of 0.1 N bromine and 20 mL of 2 A sulfuric acid, and stopper the flask. Place a few milliliters of a saturated solution of potassium iodide in the lip around the stopper, shake the flask well, and allow it to stand for 3 h. Place the flask in an ice bath for 5 min, then carefully remove the stopper, and allow the potassium iodide solution to be drawn into the flask. Add 2 g of potassium iodide dissolved in 10 mL of recently boiled water, shake the flask, and titrate the liberated iodine with 0.1 A sodium thiosulfate, using starch TS as the indicator. Each milliliter of 0.1 A bromine is equivalent to 2.311 mg of Mn(H2P02)2-... 

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. 

The triiodide ion formed is determined by spectrophotometry (352 nm), volumetric titration (against sodium thiosulfate standard solution and starch as an indicator), or coulometry. 

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