Potassium iodate reagent

Potassium iodate [7758-05-6] M 214.0, pK 0.80 (for HIO3). Crystd twice from distilled water (3mL/g) between 100° and 0°, dried for 2h at 140° and cooled in a desiccator. Analytical reagent grade material dried in this way is suitable for use as an analytical standard. 

Procedure. Weigh out accurately about 2.5 g of finely powdered mercury(II) chloride, and dissolve it in 100 mL of water in a graduated flask. Shake well. Transfer 25.0 mL of the solution to a conical flask, add 25 mL water, 2mL 1M hydrochloric acid, and excess of 50 per cent phosphorous(III) acid solution. Stir thoroughly and allow to stand for 12 hours or more. Filter the precipitated mercury(I) chloride through a quantitative filter paper and wash the precipitate moderately with cold water. Transfer the precipitate with the filter paper quantitatively to a 250 mL reagent bottle, add 30 mL concentrated hydrochloric acid, 20 mL water, and 5 mL carbon tetrachloride or chloroform. Titrate the mixture with standard 0.025M potassium iodate in the usual manner (Section 11.127). 

Schnepfe [83] has described yet another procedure for the determination of iodate and total iodine in seawater. To determine total iodine 1 ml of 1% aqueous sulfamic acid is added to 10 ml seawater which, if necessary, is filtered and then adjusted to a pH of less than 2.0. After 15 min, 1 ml sodium hydroxide (0.1 M) and 0.5 ml potassium permanganate (0.1M) are added and the mixture heated on a steam bath for one hour. The cooled solution is filtered and the residue washed. The filtrate and washings are diluted to 16 ml and 1ml of a phosphate solution (0.25 M) added (containing 0.3 xg iodine as iodate per ml) at 0 °C. Then 0.7 ml ferrous chloride (0.1 M) in 0.2% v/v sulfuric acid, 5 ml aqueous sulfuric acid (10%) - phosphoric acid (1 1) are added at 0 °C followed by 2 ml starch-cadmium iodide reagent. The solution is diluted to 25 ml and after 10-15 min the extinction of the starch-iodine complex is measured in a -5 cm cell. To determine iodate the same procedure is followed as is described previously except that the oxidation stage with sodium hydroxide - potassium permanganate is omitted and only 0.2 ml ferrous chloride solution is added. A potassium iodate standard was used in both methods. 

In the sodium borate solution containing bromide, when the pH 4 buffer is added before the potassium iodate solution, titrations give low total residual chlorine concentrations. This loss increases with the amount of stirring time between the addition of the reagents. Even for a stirring time of 10 seconds, there is a loss of about 17% of the total residual chlorine. If the solution were stirred for 30 min, 85% of the chlorine would have disappeared. The concentration of total residual chlorine determined by the reference methods does not change throughout the experiment. This implies that this loss of chlorine does not occur in the reaction vessel, but in the titration cell as a result of the analytical procedure. 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

The effects of such oxidants as a mixture of potassium iodate and dichromate in concentrated sulfuric and phosphoric acids (van Slyke reagent), hot solutions of chromic acid, and acidic solutions of ceric sulfate, permanganate, periodate, and hyperoxidized transition metals on a number of sugar derivatives has been described (Ref. 1, pp. 1151-1153). 

Copper Reagent Solution Dissolve 28 g of anhydrous dibasic sodium phosphate and 40 g of potassium sodium tartrate (KNaC4H406-4H20) in 700 mL of water. Add 100 mL of IN sodium hydroxide and 8 g of copper sulfate pentahy-drate, followed by 180 g of anhydrous sodium sulfate. Add 0.7134 g of potassium iodate, and dilute to 1 L. Allow to stand for several days, then filter the clear top part of the solution through a medium-porosity sintered-glass funnel. 

Andrews introduced the titration, further developed by Jamieson," in which potassium iodate is used as a titrating reagent. In 3 to 9 Af hydrochloric acid, iodate is reduced to iodine monochloride ... 

Potassium iodate is an excellent primary standard for thiosulfate solutions. In this application, weighed amounts of primaiy-standard grade reagent are dissolved in water containing an excess of potassium iodide. When this mixture is acidified with a strong acid, the reaction... 

Reagents The carrier stream is prepared by first dissolving 0.3 g of starch (Amidon soluble, Merck) in 250 mL of water while being heated. After cooling the starch solution is combined with a solution of 2.14 g of potassium iodate in 150 mL of water to which is added 200 mL of 1 M sulfuric acid, whereupon the volume is made to 1 L with distilled water. 

IV) may be removed together from acidic solution by precipitation with potassium iodate, but the reagent is too expensive for large-scale work. 

Potassium iodate Exactly 356.7 mg of dried (180 "C) potassium iodate (a.g.) are dissolved and made up to 1000mL. The solution is 1.667 nunol/L. (The reagent is the same as used for the determination of dissolved oxygen see Chapter 4.)... 

The sulfar-containing OP insecticides can be detected eithor with iodine-azide (149) or with potassium iodate (150) reagents. 4-(4 -nitrobenzyl)pyridine-tetraethy)enepentamine reagent is also applied for their detection (21). 

The iodine is then titrated with the thiosulfate solution as detailed in Chapter 17 (p. 516). Finally, potassium iodate is used as an oxidizing agent in the intriguing iodine clock reaction commonly used as a demonstration of limiting reagents and as a system to exemplify the determination of a rate law (see Problem 18.52). 

Alkaline Copper Iodide Reagent. In 600 ml. of warm water are dissolved 81 g. of potassium citrate (KjCoHiO/.HiO), 70 g. of potassium bicarbonate, and 92 g. of potassium oxalate (K1C2O4.H2O). A solution of 25 g. of copper sulfate (CUSO4.-5H 0) is run into the bottom of the main solution with constant stirring. To the mixture a solution of 3.57 g. of potassium iodate and 50 g. of potassium iodide in 200 ml. of water is added. The whole is cooled and made up to 1 liter. 

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