Calcium carbonate , titrations

The EGTA solution may be standardised by titration of a standard (0.05M) calcium solution, prepared by dissolving 5.00 g calcium carbonate in dilute hydrochloric acid contained in a 1 L graduated flask, and then after neutralising with sodium hydroxide solution diluting to the mark with de-ionised water, use zincon indicator in the presence of Zn-EGTA solution (see below). 

Note. A better blank is obtained by adding about 0.5 g of calcium carbonate before determining the correction. This gives an inert white precipitate similar to that obtained in the titration of chlorides and materially assists in matching the colour tints. 

Either the Mohr titration or the adsorption indicator method may be used for the determination of chlorides in neutral solution by titration with standard 0.1M silver nitrate. If the solution is acid, neutralisation may be effected with chloride-free calcium carbonate, sodium tetraborate, or sodium hydrogencarbonate. Mineral acid may also be removed by neutralising most ofthe acid with ammonia solution and then adding an excess of ammonium acetate. Titration of the neutral solution, prepared with calcium carbonate, by the adsorption indicator method is rendered easier by the addition of 5 mL of 2 per cent dextrin solution this offsets the coagulating effect of the calcium ion. If the solution is basic, it may be neutralised with chloride-free nitric acid, using phenolphthalein as indicator. 

Oscillometry 527 as analytical tool, 528 titrations (H.F.), 527 Osmium tetroxide catalyst 381 Ostwald s dilution law 31 Ovens electric, 97 microwave, 97 Overpotential 506 Overvoltage see Overpotential Oxalates, D. of as calcium carbonate via oxalate, (g) 484... 

They used the titration method of Tsunogai et al. [157]. The titrant solutions were standardised against calcium carbonate of primary standard quality (99.9975% purity) rather than zinc, and the EGTA (Eastman Chemicals) was used without further purification. 

What is the titer (expressed in milligrams per milliliter) of a solution of disodium dihydrogen ethylenediaminetetraacetate (EDTA) with respect to calcium carbonate if 17.29 mL of it was needed to titrate 0.0384 g of calcium carbonate ... 

It may seem strange that we would ever want to perform an experiment of this kind. First of all it would be used in the event of a slow reaction taking place in the reaction flask. Perhaps the sample is not dissolved completely, and addition of the titrant causes dissolution to take place over a period of minutes or hours. Adding an excess of the titrant and back-titrating it later would seem an appropriate course of action in a case of this kind. An example would be the determination of the calcium carbonate in an antacid tablet (Experiment 13). 

Why is a back titration useful in the analysis of an antacid tablet containing calcium carbonate as the active ingredient ... 

Calcium carbonate is not soluble in water. The addition of the standard acid to a tablet immersed in water causes it to dissolve, but rather slowly. A direct titration is not appropriate because the reaction is not fast, and it would be difficult to detect the end point. A back titration is therefore useful because the standard acid can be added in excess so that the calcium carbonate completely dissolves. The excess acid can then be titrated with a standard base. 

After equilibrium, filtration, and pH adjustment, the residual calcium ion concentration was then titrated by EDTA solution. A higher residual calcium ion concentration indicates better inhibition activity and, therefore, more effectiveness in controlling calcium carbonate deposition in the treated water. As shown in Table III, at dosages of 1 to 5 ppm, the polyacrylic acid was more effective than the acrylic acid/N-(hydroxyalkyl)-acrylamide copolymers. 

The TEB value may be obtained by either the sum of the individually measured cations or by evaporating and igniting a portion of the ammonium ethanoate leachate to convert the metallic cations to oxides and carbonates, followed by addition of excess acid (to convert carbonates to chlorides) and back-titration with alkali. The latter method is difficult if the soil is insufficiently base-rich to provide an adequate amount of bases for the titration. On the other hand, the calcium carbonate in calcareous soils may be partially leached by the ammonium ethanoate at pH 7.0 in addition to the exchangeable bases and thus give an exaggerated TEB value and a percentage base saturation in excess of 100%. The TEB by ignition/titration can serve as a check on the values from the summation method. 

The lithium carbonate concentration was measured by acidimetric titration with methyl orange indicator. The calcium sulfate and calcium hydroxide concentrations were determined by titration with disodium dihydrogen Versenate [the disodium salt of (ethylenedinitrilo) tetraacetic acid], with added magnesium chloride. A buffer of ammonium chloride in ammonium hydroxide was employed. The indicator was Erio-chrome Black T. A special high purity calcium carbonate in hydrochloric acid was used as a standard. Because of the high concentration of sodium sulfate it was con-... 

The USP [2] describes a method for the titration of EDTA, using a weighed amount of chelometric standard calcium carbonate previously dried. The weight of edetate disodium (in mg) is calculated using the following formula ... 

Papers which are acidic as manufactured can be stabilized by a deacidification procedure. Several processes have been developed for this purpose, the most successful of which provide neutralization of the acid present and leave a residue such as calcium carbonate or magnesium carbonate as reserve alkalinity in the paper. This alkalinity serves to protect the paper as acidity develops from paper components during aging or is introduced by atmospheric contamination. The amount of reserve alkalinity can be determined by adding a measured volume of standard acid solution in excess to a weighed specimen of the paper and back-titrating the excess to neutrality with standard base solution. 

The anaerobic fermentation of lactic acid is traditionally performed at up to 50°C over 2-8 d at pH 5.5-6.5 (lactic acid bacteria are highly sensitive to acid). The pH is maintained by titration with a base, usually calcium carbonate. The product concentration is kept below approx. 100 g L 1 to prevent precipitation of calcium lactate, as the separation of a precipitate from the biomass would be too elaborate. The stoichiometric yields are high, of the order of 1.7-1.9 mol mob1 (85-95% of the theoretical yield) but the space-time yield, which is ap-... 

Carbonate alkalinity is not a directly analyzable quantity, but it can be derived from the titration alkalinity (A ) by a relationship which is temperature and pressure dependent. pH is also variable with pressure and temperature. In addition, pH can be defined several ways depending on which buffer system is used, whether liquid junction potentials are considered, and what definition of ionic strength is used. The values of the apparent dissociation constants and calcium carbonate solubility constants are dependent on exactly what definition of seawater pH is used and what standardization technique is used (15, 16, 17). 

Determination of Chlorosulphonic Acid. About i gm. of the sample is introduced into a small glass bulb which is then sealed in the flame and weighed accurately. This bulb is then placed in a tall glass cylinder of about 150 ml. capacity, containing about 100 ml. water. The cylinder is stoppered tightly and shaken violently so as to break the bulb, and then allowed to stand until the cloud which first forms in the cylinder completely disappears. The contents are then transferred to a 500 ml. flask and made up to volume. 200 ml. of the solution are then titrated with a decinormal sodium hydroxide solution, to the methyl-orange end-point, so as to obtain the total hydrochloric and sulphuric acid content. In another 200 ml. the hydrochloric acid is titrated with a decinormal solution of silver nitrate in presence of a few drops of potassium chromate solution, after addition of excess of pure calcium carbonate. 

Numerous tertiary amines that also contain carboxylic acid groups form remarkably stable chelates with many metal ions. Ethylenediamine tetra-acetic acid (EDTA) can be used for determination of 40 elements by direct titration using metal-ion indicators for endpoint detection. Direct titration procedures are limited to metal ions that react rapidly with EDTA. Back titration procedures are useful for the analysis of cations that form very stable EDTA complexes and for which a satisfactory indicator is not available. EDTA is also used for determining water hardness the total concentration of calcium and magnesium expressed in terms of the calcium carbonate equivalent. 

Calcium Carbonate. Ten g. of nitrocellulose, 100 c.c. of N hydrochloric acid and too c.c. water are put into a stoppered cylinder, shaken for an hour, and the excess of acid titrated with N o sodium carbonate, using methyl orange as indicator. 

The best way to illustrate the procedures adopted for back and blank titrations is to consider an example, the determination of chalk, or calcium carbonate, CaC03. Chalk is used as an antacid and indigestion remedy, particularly in children, and is official in the British Pharmacopoeia as the powder and the mixture (Paediatric Chalk BP). 

Calcium carbonate (CaC03) is found in some commercial antacids (materials used to decrease the amount of acid in the stomach). A 0.5 g sample of antacid is titrated with hydrochloric acid ... 

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