Chlorine, free, determination

A sample from a public water supply is analyzed to determine the free chlorine residual, giving an absorbance of 0.113. What is the free chlorine residual for the sample in parts per million CI2 ... 

Apart from added stabilizers, commercial grades of trichloroethylene should not contain mote than the following amounts of impurities water 100 ppm acidity, ie, HCl, 5 ppm insoluble residue, 10 ppm. Free chlorine should not be detectable. Test methods have been estabUshed by ASTM to determine the following characteristics of trichloroethylene acid acceptance, acidity or alkalinity, color, corrosivity on metals, nonvolatile-matter content. 

We proposed new photometric reagent 4,4 -bis(diethylamino)-thiobenzophenone (ethyl derivative of Michler s thioketone, EMT) for the determination of free chlorine and chloramines in drinking water. 

Other methods for the determination of chlorine in seawater or saline waters are based on the use of barbituric acid [13] and on the use of residual chlorine electrodes [ 14] or amperometric membrane probes [15,16]. In the barbituric acid method [12], chlorine reacts rapidly in the presence of bromide and has completely disappeared after 1 minute. This result, which was verified in the range pH 7.5-9.4, proves the absence of free chlorine in seawater. A study of the colorimetric deterioration of free halogens by the diethylparaphenylene-diamine technique shows that the titration curve of the compound obtained is more like the bromine curve than that of chlorine. The author suggests... 

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. 

Free chlorine reacts with N,N-( 1-naphthyl)-1,2-ethylendiamine hydrochloride (at pH 6.2-6.5) to form a red compound, which is determined at 510 nm... 

International Standard Organization. 1985. Water quality. Determination of free chlorine and total chlorine. Part 1 Titrimetric method using A,IV-diethyl-l,4-phenylenediaimne. ISO 7393-1. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

It is not the same as calcium hypochlorite, which contains over 99 percent, available chlorine. (The term available chlorine refers to the oxidizing power of a bleach equivalent to that of free chlorine, as determined by the standard acidic-KJ-thiosulfate titration.)... 

Industrial liquid chlorine is routinely analyzed for moisture, chlorine, other gaseous components, NQ 3, and mercury following established procedures (10,79) Moisture and residue content in liquid chlorine is determined by evaporation at 20°C followed by gravimetric measurement of the residue. Free chlorine levels are estimated quantitatively by thiosulfate titration of iodine liberated from addition of excess acidified potassium iodide to the gas mixture. 

Example 17.8 Referring to Figure 17.1, if a dosage of 1.8 mg/L is administered, determine the amount free chlorine residual that results, the amount of combined residual that results, and the amount of combined ammonia chloramine residual that results. Also, determine the amount of organic chloramine residual that results. 

When plant tissues are treated with chlorine and subsequently with a hot 95% alcohol solution containing three per cent monoethanolamine, a residue is obtained containing the complete carbohydrate fraction of these materials and known as holocellulose. This method serves as a very convenient means of obtaining plant materials lignin-free for determining the relationship existing between the various carbohydrate fractions. 

Because, with free chlorine, a 1-log Giardia inactivation provides greater than a 4-log virus inactivation, inactivation of Giardia is the controlling factor for determining overall reductions. 

A military specification [1394a] suggests the determination of phosgene by reaction of phosgene with a solution of sodium iodide in propanone, and titration of the liberated iodine with sodium thiosulfate (see Section 3.2.1.2), correcting for any free chlorine present. 

When free chlorine is determined in tap water, a sample of water is placed in a still (with no oxidizer) and chlorine is distilled, along with some water, into a reeeiver containing Methyl Red. The sample water may also be added directly to a Methyl Red solution. 

Benzidine immobilized on cellulose and silica gel can be used for the determination of free chlorine (0.05-0.5 mg l ) in waters [1]. Free and combined chlorine in water and chlorine in air were determined using solid-phase extraction and azo dye formation [2]. Combined chlorine in water could be determined after masking the free chlorine with acetone. 

Crosslinked chloromethylated PS beads were reacted with hydantoin and imidazolidinone derivatives to produce functionalised beads which could be rendered biocidal by reaction with free chlorine or bromine. The biocidal efficacies of the N-chlorinated and, in one case, the N-brominated polymeric beads against Staphylococcus aureus or Escherichia coli 0157 H7 in aqueous suspension were determined. The N-halogenated polymeric beads were effective in aqueous disinfection application, requiring short contact times for inactivation of the two bacteria. The functionalised polymers could be tailored to the application, depending on whether rapid biocidal activity or long-term stability to loss of oxidative halogen was desired. 11 refs. (Pt.III, ibid, p.363-7)... 

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