Determination of Hypochlorites

Bleaching solutions are aqueous sodium hypochlorite. One example is Javel water in France. It can be prepared by reacting chlorine with a solution of sodium 

Javel water may be considered a mixture of equal quantities of sodium hypochlorite and sodium chloride. Concentrated and more diluted solutions are commercially available. The latter are called ordinary Javel waters. For pharmaceutical use, there is Dakin solution, which is a diluted Javel water to which has been added some sodium hydrogen carbonate to weaken the alkaline character of the solution, which is irritating for tissues. 

Calcium hypochlorite is prepared by reacting chlorine with calcium hydroxide according to 

This is the reason why it is improperly called slaked lime chloride. Actually, the commercial calcium hypochlorite is essentially a mixture of calcium hypochlorite (sensu stricto) and basic calcium chloride, that is, in fact, Ca(C10)2, CaCl2, and Ca(OH)2, H2O. It is used as a white powder called bleaching powder.  

Recall (Chap. 15, Fig. 15.12) that the species HCIO, C10 , and CI2 are not stable in water. They oxidize it. However, the reactions are slow. This is the reason why neutral and alkaline hypochlorite solutions exhibit some undeniable stability despite their strong oxidizing properties. Oxidization of water by hypochlorous acid and by hypochlorites is written as follows according to the pH value  

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A quantitative method of determination of hypochlorites in the presence of chlorine by using the KI method, is given in Scott (Ref 5,... 

Adam, L.C. and Gordon, G. (1995) Direct and sequential potentiometric determination of hypochlorite, chlorite, and chlorate ions when hypochlorite ion is present in large excess. Anal. Chem. 67, 535-540. 

In order to demonstrate the principles of flow analysis, classical spectrophotometric determinations, including a pseudo-flow titration, were carried out in the very first flow injection analyser [408]. More recently, the determination of hypochlorite in bleaching products using natural flower extracts [409] has also been exploited. 

L.A. Ramos, K.R. Prieto, E.T.G. Cavalheiro, C.C.S. Cavalheiro, Determination of hypochlorite in bleaching products with flower extracts to demonstrate the principles of flow injection analysis, J. Chem. Educ. 82 (2005) 1815. 

A. G. Fogg, A. Y. Chamsi, A. A. Barros, and J. O. Cabral, Flow Injection Voltammetric Determination of Hypochlorite and Hypobromite as Bromine by Injection into an Acidic Bromide Eluent and the Indirect Determination of Ammonia and Hydrazine by Reaction with an Excess of Hypobromite. Analyst, 109 (1984) 901. 

A. Y. Chamsi and A. G. Fogg, Application of the Reductive Flow Injection Amperometric Determination of Iodine at a Glassy Carbon Electrode to the lodometric Determination of Hypochlorite and Hydrogen Peroxide. Analyst, 111 (1986) 879. 

The determination of hypochlorites is based on their oxidizing power. Two reductors are used ... 

An interesting example of selective analysis operations is provided by the determination of hypochlorite C10 , chlorite C102 (Cl-t-III), and chlorate ions in admixture. This is a mixture encountered in a bleaching powder due to the disproportionation of hypochlorite, transformation - -I - -V that is achieved through... 

Laundry bleach is a solution of sodium hypochlorite (NaCIO). To determine the hypochlorite (CIO-) content of bleach (which is responsible for its bleaching action), sulfide ion is added in basic solution. The balanced equation for the reaction is... 

Determination of sulphite by oxidation to sulphate and precipitation as barium sulphate Discussion. Sulphites may be readily converted into sulphates by boiling with excess of bromine water, sodium hypochlorite, sodium hypobromite, or ammoniacal hydrogen peroxide (equal volumes of 20-volume hydrogen peroxide and 1 1 ammonia solution). The excess of the reagent is decomposed by boiling, the solution acidified with hydrochloric acid, precipitated with barium chloride solution, and the barium sulphate collected and weighed in the usual manner (Section 11.72). 

In the amperometric titration for the determination of total residual chlorine in seawater, tri-iodide ions are generated by the reaction between hypochlorite and/or hypobromite with excess iodide pH 4 (reactions (4.3) and (4.4)). The pH is buffered by adding a pH 4 acetic acid-sodium acetate buffer to the sample. 

Berg and Addullah [47] have described a spectrophotometric autoanalyser method based on phenol, sodium hypochlorite, and sodium nitroprusside for the determination of ammonia in sea and estuarine water (i.e., the indophenol blue method). 

Le Corre and Treguer [49] developed an automated procedure based on oxidation of the ammonium ion by hypochlorite in the presence of sodium bromide followed by spectrophotometric determination of the nitrite. The standard deviation on a set of samples containing 1 p,g NH -N per litre was 0.02. This method was compared with an automated method for the determination of ammonia as indophenol blue. The results from the two methods are in good agreement. 

Emmet RT (1969) Spectrophotometric determination of urea in natural waters with hypochlorite and phenol. NAVSHIPRANDLAB Annapolis Report 2663... 

The amount of hypochlorite ion present in bleach can be determined by an oxidation-reduction titration. In this experiment, an iodine-thiosulfate titration will be utilized. The iodide ion is oxidized to form iodine, I2. This iodine is then titrated with a solution of sodium thiosulfate of known concentration. Three steps are involved ... 

In this step the reddish brown color of the triiodide begins to fade to yellow and finally to clear, indicating only iodide ions present. However, this is not the best procedure for determining when all of the I3 has disappeared since it is not a sensitive reaction and the change from pale yellow to colorless is not distinct. A better procedure is to add a soluble starch solution shortly prior to reaching the end point, since if it is added to soon, too much iodine or triiodide ion may be present forming a complex that may not be reversible in the titration. The amount of thiosulfate is proportional to the amount of hypochlorite ion present. 

Kinetic and mechanistic studies of hexacyanoferrate(II) reductions include those of hypochlorite, of peroxodisulfate (for which activation volumes were determined), and of trart5-[Co(salen)(H20)2] (salen = A,A -ethylenebis(salicylideneaminate), (37)). Peroxonitrite oxidation of hexacyanoferrate(II) is first-order in peroxonitrite, zeroth-order in hexacyanoferra-te(II). The inference that the rate-limiting step in this reaction is decomposition of the oxidant is supported by activation volume data - the value of A for oxidation of hexacyanoferrate(II), -fllcm moU lies within the range established for peroxonitrite decomposition but is very different from the value of AF, -7cm moU ... 

Weatherburn, M. W., Phenol-Hypochlorite Reaction for Determination of Ammonia, Anal. Chem.., 39, 971-974 (1967). 

Methods of determination of hypochlorous acid and hypochlorites are given in Ref 2, pp 292-296... 

Kankakee Ordnance Works, Joliet, Illinois 0953) 12)A.Lamouroux,MP 37,439—50 (1955) (Colorimetric micro-determination of ammonia, utilizing the intense blue coloration produced on treatment of its aq soln with phenol and hypochlorite) 13) A.M.P.TansjChemEduc 62,218(1955)... 

C. Ammonia can be determined spectrophotometrically by reaction with phenol in the presence of hypochlorite (OC1) ... 

The concentration of hypochlorite ions in a solution can be determined by adding a sample of known volume to a solution containing excess I- ions, which are oxidized to iodine ... 

A method for the determination of chlorate in water extracts of soil is based on its conversion to free chlorine upon reaction with hydrochloric acid, followed by spectrophotometric evaluation of chlorine at 448 nm by the spectrophoto-metric o-toluidine method [9]. A correction is made for interference by iron (III), nitrite, free chloride derived from hypochlorites and strong oxidising agents by subtracting the absorbance of a modified blank, containing a lower concentration of hydrochloric acid, from that obtained in the test. 

TOX, EOX, AOX, and POX were determined in hospital waste sludge138 treated with 400 pg g 1 of hypochlorite. Ethanol is a solvent commonly used for extracting organic halides from sludge, but its extraction efficiency proved to be poor. 

Kagaya, S., Y. Kuroda, Y. Serikawa, and K. Hasegawa. 2004. Rapid determination of total mercury in treated waste water by cold vapor atomic absorption spectrometry in alkaline medium with sodium hypochlorite solution. Talanta 64 554-557. 

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