Total chlorine residuals

This is an indirect method of analysis because the chlorine-containing species do not react with the titrant. Instead the total chlorine residual oxidizes l to l3 , and the amount of 13 is determined by the redox titration with Na282 03. 

One of the most important applications of redox titrimetry is in evaluating the chlorination of public water supplies. In Method 9.3 an approach for determining the total chlorine residual was described in which the oxidizing power of chlorine is used to oxidize R to 13 . The amount of 13 formed is determined by a back titration with 8203 . 

Until progress can be made in development of practical and affordable online contaminant monitoring and surveillance systems, most chemical industrial facilities must use other approaches to contaminant monitoring and surveillance. This includes monitoring data of physical and chemical contamination surrogates, pressure change abnormalities, free and total chlorine residual, temperature, dissolved oxygen, and conductivity. 

Then, after the process of disinfection, and after the reactions with reduced organic and inorganic matter (including NH3) take place, the total available chlorine (or total chlorine residual) is given by the sum of the free available chlorine and the combined available chlorine. ... 

Determination of Total Chlorine Residuals (lodometric Method)... 

The amount of the combined chlorine residuals thus decreases along the curve CD. Point D indicates almost complete decomposition of chloramines. At this stage, known as Break-point Chlorination, there is marked decrease in the residual chlorine ( a minimum in the curve). A higher dosage of chlorine appears as free chlorine residuals and total chlorine residuals start increasing. This is shown by the part DE of the curve. 

The methods described earlier for determining the total, free, or combined chlorine residual also are used in establishing the chlorine demand of a water supply. The chlorine demand is defined as the quantity of chlorine that must be added to a water supply to completely react with any substance that can be oxidized by chlorine while also maintaining the desired chlorine residual. It is determined by adding progressively greater amounts of chlorine to a set of samples drawn from the water supply and determining the total, free, or combined chlorine residual. 

The (9-cresol novolaks of commercial significance possess degrees of polymerization, n, of 1.7—4.4 and the epoxide functionaUty of the resultant glycidylated resins varies from 2.7 to 5.4. Softening points (Durran s) of the products are 35—99°C. The glycidylated phenol and o-cresol—novolak resins are soluble in ketones, 2-ethoxyethyl acetate, and toluene solvents. The commercial epoxy novolak products possess a residual hydrolyzable chlorine content of <0.15 wt% and a total chlorine content of ca 0.6 wt % (Table 2). 

The bound chloiine formed does not readily saponify with metal hydroxide solutions and is analyzed as part of the total chlorine of the resin. (3) Incomplete dehydrohalogenation which results in residual saponifiable or hydrolyzable chlorine ... 

The total-chlorine method has been used extensively in the determination of spray residues of the chlorinated hydrocarbons 56). Usually the kind of insecticide applied has been known, and by means of the proper factor the chlorine values could be calculated to the insecticide originally used. This calculation is not entirely valid, as the determinations do not differentiate between the insecticide and its degradation products or other contaminants containing organic chlorine. The values obtained by the total-chlorine method are useful, however, because they indicate the magnitude of the residue and the analysis can be made in a short time with standard laboratory equipment. 

The total-chlorine method for determining residues of benzene hexachloride, chlordan, and toxaphene has also been used 55) in experiments where it was known that these insecticides had been applied. With benzene hexachloride, which is known to give off-flavor to some crops, it has not been demonstrated that a relation between organic chlorine values and off-flavor exists. In fact, in most cases where off-flavor was attributed to benzene hexachloride, it has not been possible to detect organically bound chlorine. 

The total-chlorine method for residues of the chlorinated hydrocarbons has also been applied to animal tissues, milk, and dairy products (9). As in the spray-residue determinations, the method does not differentiate between the insecticide and metabolites. 

Recently it was shown that when DDT, benzene hexachloride, or toxaphene is fed or applied to cattle, such organic chlorine residue as may be present in the fatty tissues consists essentially of unchanged insecticide. Carter (12) demonstrated their presence by separating the fats and other oxygenated products with sulfuric acid-sodium sulfate mixture and determining total chlorine. In experiments with DDT Schechter (46) demonstrated its presence in fatty tissue and in butterfat by the Schechter-Haller colorimetric method (47). The residues were then tested for toxicity to houseflies in comparison with the known insecticides of the same concentration. In both cases the known insecticide gave the same mortality as the residue. 

Parathion analyses were made by the method of Averell and Norris (I). DDT residues were determined at Vincennes by the total-chlorine method of Wichman et al. (4), and at Yakima by the colorimetric method of Stiff and Castillo (3), as modified by the Food and Drug Administration (2). 

The residual portion of the total chlorine in a cooling system after the chlorine demand has been satisfied by the addition of chlorine in some form. Usually a combination of hypochlorite ions (OC1 ) and hypochlorous acid (HOC1) and measured by diethyl-p-phenylene diamine(DPD) method. Operators frequently add chlorine once per day for several hours to provide a free chlorine reserve of 0.1 to 0.3 ppm. 

When granular metallic iron smaller than 0.5 mm was used, an optimum reaction rate was obtained. The ratio of metallic iron to hypochlorite concentration was approximately 1.1-fold in terms of the stoichiometric ratio. The contact time of granular metallic iron with chlorinated water was approximately 25 min thus, at pH less than 7, the chlorine residues were totally removed within 25 min from the beginning of the reaction. 

During combustion of the coal, organic chlorides are decomposed and liberate the chlorine atom as hydrochloric acid, while inorganic chlorides decompose with evolution of hydrochloric acid and ultimately leave a residue of the metallic oxide. Since approximately half the chlorine in coal occurs as inorganic chloride and the remainder as inorganic chloride, a correction for the chlorine present originally as inorganic material is easily applied when the total chlorine is known. 

Total chlorine is the sum of free and combined chlorine (defined as the residual chlorine existing in water in chemical combination with ammonia or organic amines). Total chlorine reacts with V,V-(l-naphthyl)-l,2-ethylendiamine hydrochloride and potassium iodide the compound formed is titrated as stated above. 

Lindane is relatively non-persistent, especially under anaerobic conditions, and although its more highly chlorinated residues may present the same problems as those of polychlorophenols, the less chlorinated residues should follow pathways similar to those established for the microbial degradation of the chlorinated phenoxyalkanoic acid herbicides. Recent evidence (46) indicates that certain microbes can dechlorinate DDT anaerobically, thereby making available intermediates which may undergo further aerobic attack, leading in principle to total degradation. The ultimate fate of the hexachloronorbornene nucleus of cyclodienes is still uncertain and this question continues to attract attention. 

The chlorine residual may be either a free available residual, a combined available residual, or a combination of the two. Free available chlorine refers to the total concentration of hypochlorous acid and hypochlorite ions. Combined available chlorine is the total concentration of mono- and dichloramines, plus nitrogen trichloride and organic nitrogen chlorine-containing compounds (1). 

The stabilized sludge will have a pH of 2.5. 5 and chlorine residual of 200 00 mg/L. The stabilized sludge will have chlorine smell and light brown color. Total solids, suspended solids, and volatile solids concentrations will be about the same as the raw sludge. When stored for 48 h, the chlorine residual will have fallen to 0 and the pH will have increased to 4.5-6.0. The organics will normally not decompose even after several days of storage. 

Molecular chlorine, CI2, is an ideal chemical for delignification as it is cost-efficient and has reasonable selectivity, well capable of removing 75-90% of the residual lignin in a single stage. However its undesirable effects - waste water with chlorides that is corrosive, and a tiny by-product of chlorinated organic compounds -means that molecular chlorine has been abandoned entirely in some countries and where it is still used this is often in conjunction with chlorine dioxide (D) whose environmental footprint is some 2.6 times smaller. Today, more than 75% of pulps are bleached without any molecular chlorine. These are described as elemental chlorine-free (ECF). Only c. 6% of bleached pulps are total chlorine-free (TCF),... 

Oxidant residuals in the form of total residual chlorine were first reported by the New York State Department of Environmental Conservation in rainfall and lake waters of the Western Adirondacks of New York State in 1976-77. Chlorine residuals analyzed by the orthotoline colorimetric procedure developed by Palin (1957) were detected in rainfall at Boonville and Stillwater, New York and in Echo Lake, Hinckley Reservoir and Stillwater Reservoir (Figure 2. Total residual chlorine in rainfall near Boonville, New York... 

Lamb (1978) introduced chlorine into a trout stream in Central New York to evaluate the toxicity to various stream organisms. Periphyton density was reduced only at high chlorine residuals fish were sensitive to low concentrations and total residual chlorine concentrations of less than 0.01 mg/1 caused catastrophic drift of sensitive stream insects. 

Test methods. The same direct and indirect test methods used for the measurement of chlorine residual can be used for measuring total bromine. The results of the chlorine assays must be multiplied by a factor of 2.25 to account for the differenee in the chlorine and bromine molecular weights. In bromine systems the only active reported is the total bromine. This is a reflection that combine bromine (bromamine) is efficacious. 

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