Carbon tetrachloride, titration

Andrews deration An important titration for the estimation of reducing agents. The reducing agent is dissolved In concentrated hydrochloric acid and titrated with potassium iodale(V) solution. A drop of carbon tetrachloride is added to the solution and the end point is indicated by the disappearance of the iodine colour from this layer. The reducing agent is oxidized and the iodate reduced to ICl, i.e. a 4-eiectron change. 

Thiosulfate titration of iodine is limited to an iodine concentration of 7.5 fig/mL (69). The use of organic solvents such as benzene, toluene, chloroform, and carbon tetrachloride as indicators in the titration of iodine have been proposed (70—72). These procedures increase the sensitivity of the titration so that 6.0 fig/mL of iodine can be detected, although a sensitivity of 2 fig/mL has been claimed (73). 

Alternatively, in this and all subsequent titrations with 0.025M potassium iodate, a 250 mL conical flask may be used and the carbon tetrachloride or chloroform indicator replaced by 0.5 mL amaranth or xylidine ponceau indicator, which is added after most of the iodine colour has disappeared from the reaction mixture (see Section 10.125). 

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). 

The adsorption of block and random copolymers of styrene and methyl methacrylate on to silica from their solutions in carbon tetrachloride/n-heptane, and the resulting dispersion stability, has been investigated. Theta-conditions for the homopolymers and analogous critical non-solvent volume fractions for random copolymers were determined by cloud-point titration. The adsorption of block copolymers varied steadily with the non-solvent content, whilst that of the random copolymers became progressively more dependent on solvent quality only as theta-conditions and phase separation were approached. 

In actual practice, either carbon tetrachloride or chloroform is usually added so as to make the endpoint distinctly visible. Iodine is liberated at the initial stages of the titration which renders the chloroform layer coloured. At that material point when all the reducing agent under estimation has been duly oxidized, the iodate completes the oxidation of iodine and iodide to I+, and hence the colour from the chloroform layer disappears. 

Take the 250-mi volumetric flask contg material extracted by carbon tetrachloride as shown here under H- Analytical Procedures, step 1, and transfer from it 25 ml (using a calibrated pipet, previously rinsed with CC14 and dried, to the titration flask F, Evaporate the CC14 to dryness with a slow stream of air and then sweep the air off with a stream of C02 from a cylinder (or from a Kipp generator). While continuing to pass C02 thru the flask, introduce... 

To determine the purity of any sample of allyl alcohol, 1 cc. is run into 15 to 25 cc. of carbon tetrachloride and this solution is then treated in the cold with a carbon tetrachloride solution of bromine (standardized with potassium iodide and sodium thiosulfate) until a permanent bromine coloration is obtained. The amount of allyl alcohol present in any solution may also be determined roughly by conversion to allyl bromide. From several experiments it was found that the allyl bromide obtained was equivalent to the amount of allyl alcohol as determined by bromine titration. 

After drying over 10 g. of anhydrous potassium carbonate, the oil is decanted and fractionated through an 80-cm. Vigreux column at atmospheric pressure. Crotyl alcohol distils at 117-122°/760 mm., weight 130 g. (60%). This material is 93% pure as determined by titration with bromine in carbon tetrachloride. If the crude crotyl alcohol is dried for several days before distillation the product is 97% pure. Refractionation through a 110-cm. bead column gives material boiling at 121.2°/760 mm. which is 99.1 to 99.7% pure. 

Deactivation by solvents may be considered as an extreme case of deactivation by a foreign gas. Several experiments were carried out in a carbon tetrachloride solution of nitrogen pentoxide and nitrogen dioxide. The decomposition was followed in two ways by the evolution of oxygen gas from the solution, and by titration of the nitrite produced when the carbon tetrachloride solution is shaken with a dilute alkali solution. The gas evolution gave more accurate results. Great precautions were necessary to keep out every trace of moisture. 

The bromination of cinnamic acid dissolved in carbon tetrachloride or other inert solvent.offers a convenient system for study. The dibromocinnamic acid produced remains in the carbon tetrachloride solution. The thermal reaction is so slow that it can barely be measured at room temperature and it is entirely negligible in comparison with the photochemical reaction at ordinary intensities. The quantum yield is so large that considerable reaction occurs even if the intensity of light is much reduced by the monochromator or other device for confining the light to a narrow range of frequencies. Furthermore, the reaction is easily and accurately followed by titration with sodium thiosulfate. Potassium iodide is added and the iodine liberated is a measure of the remaining bromine. 

If the solution is titrated with standard sodium thiosulphate solution, the total concentration of the iodine, both as free I2 and combined as IJ, is obtained, since, as soon as some iodine is removed by interaction with the thiosulphate, a fresh amount of iodine is liberated from the tri-iodide in order to maintain the equilibrium. If, however, the solution is shaken with carbon tetrachloride, in which iodine alone is appreciably soluble, then the iodine in the organic layer is in equilibrium with the free iodine in the aqueous solution. By determining the concentration of the iodine in the carbon tetrachloride solution, the concentration of the free iodine in the aqueous solution can be calculated from the known distribution coefficient, and therefrom the total concentration of the free iodine present at equilibrium. Subtracting this from the total iodine, the concentration of the combined iodine (as Ij) is obtained by subtracting the latter value from the initial concentration of potassium iodine the concentration of the free KI is deduced. The equilibrium constant ... 

Rates of Fragmentation. The solvent dependence was studied first (Table IV). Solutions of styrene ozonide were stored at 50°C. At various intervals, samples were quenched with ice water, and the acid formed was titrated with 0.051V KOH, using phenolphthalein indicator. While the ozonide was stable in benzene, carbon tetrachloride, and chloroform... 

Burton and Praill were the first to prqjare this ecies both by the interaction of perchloric acid with acetic anhydride and the metathetic reaction of sflver perchlorate with acetyl chloride , in a comprehensive study of acylation reactions. They did not attempt a characterisation of the compound and assumed that in acid solutions it existed in a fully ionised form. A few years later, Jander and Surawski followed the formation of acetyl perchlorate in acetic anhydride by measuring the electrical conductivity changes which took place when acetyl bromide was added to silver perchlorate or vice versa. In both titrations an inflection point was observed for a mixture of equimolar quantities of the two reactants indicating the formation of acetyl perchlorate. Moreover, it was clearly drown that this compound was at least partly ionised since its conductivity was higher than that of acetyl bromide. Avedikian and Commeyras characterised acetyl perchlorate by infrared and Raman spectroscopy both in acetic anhydride and carbon tetrachloride. They concluded that some ionisation was present but could not assess its extent. Molecular acetyl perchlorate was also detected. As far as we are aware, no other study of the structure and extent of dissociation of acetyl perchlorate in solution has been conducted. 

If a gas is soluble in a suitable solvent, and the concentration of the solution can be determined by a simple analytical technique, then accurately measured quantities of the gas can be dispensed by using the appropriate volume of the solution. For example solutions of the hydrogen halides in various solvents can be determined by simple acid/base titration and solutions of chlorine in carbon tetrachloride can be determined by addition of excess potassium iodide and back titration with sodium thiosulphate. Refer to textbooks of inorganic analysis for details of these methods. 

Clark and Tedder have studied the fluorination of carbon tetrachloride by flowing together F2 and CCI4, both diluted in nitrogen. FCl was converted to HF and HCl followed by titration of fluoride and spectrophotometric determination of the chloride. Experiments at 20 °C are interpreted in terms of the mechanism... 

Smith and Kurtz ° devised a titration flask with a raised bottom and a gas-entry tube. By addition of carbon tetrachloride or chloroform the reduced solution was separated from the liquid amalgam, and the titration could be carried out without draining off the amalgam. An inert atmosphere could be introduced through the gas-entry tube. 

The iodine is extracted with carbon tetrachloride (once with 20 ml. and four times with 10 ml.) and all the extracts are added to 100 ml. distilled water. The mixture is shaken to wash the tetrachloride, the water separated and shaken with a little carbon tetrachloride which is then added to the main bulk of the tetrachloride. The solution of iodine is finally titrated with thiosulphate and starch solution. 

The 100 ml. of carbon tetrachloride are decanted from the flask, the latter washed with a little carbon tetrachloride which is then added to the main bulk of tetrachloride and the free iodine in the whole titrated. 

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