Indicator Solutions

Calcon Dissolve 0.2 g of the dyestuff (sodiutn-l-(2-hydroxy-l-naphthylazo)-2-naphthol-4-sulphoiiate] in SO ml of methanol. 

15 g of DPD sulphate pentahydrate or 0.11 g of anhydrous DPD sulphate in boiled-out distilled water containing 1 ml of dilute sulphuric acid (1 part H2SO4 + 3 parts water) and 20 mg EDTA. Dilute to 100 mi. 

Eriochrome Black T Dissolve 0.2 g of the solid dyestuff in 15 ml of triethanolamine and 5 ml ethanol or dissolve 0.5 g of the dyestuff in 100 ml rectified spirit. 

Ferric alum Dissolve 25 g of Fe2(S04)3 (NH4)2S 04-24 H2O in about 100 ml of hot distilled water. Add 10 ml of A.R. HNOj, boil (until Ore reddish brown colour changes to yellow) to expel nitrous acid. Cool and filter. 

Ferroin Dissolve 1.485 g of o-phenanthroline monohydrate and 0.695 g FeS04 7H20 in boiled-out distilled water and dilute to 100 ml. (The indicator solution itself may be purdiased from tire market). 

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Composition of Indicator Solution p/ Acid Alkaline Notes... 

Name pH Range Color Change Acid to Base Indicator Solution... 

Indicator solutions 1, 1% solution in ethanol 2, 0.1% solution in ethanol 3, 0.05% solution in 90% ethanol 4, sodium or potassium salt in distilled water 5, 0.2% solution in 70% ethanol 6, distilled water. 

Use acid-base indicator solutions. Oxidation causes bleaching of indicator to colorless... 

Pyrocatechol Violet Indicator Solution. Dissolve 0.1 g of the solid dyestuff in 100 mL of water. 

Indicator solutions a number of indicator solutions are listed in this section under the names of the indicators e.g., alizarin, aurin, azolitmin, et al., which follow alphabetically. See also various index entries. 

The purity of a sample of Na2S203 was determined by a coulometric redox titration using as a mediator, and as the titrant. A sample weighing 0.1342 g is transferred to a 100-mL volumetric flask and diluted to volume with distilled water. A 10.00-mL portion is transferred to an electrochemical cell along with 25 mL of 1 M KI, 75 mL of a pH 7.0 phosphate buffer, and several drops of a starch indicator solution. Electrolysis at a constant current of 36.45 mA required 221.8 s to reach the starch indicator end point. Determine the purity of the sample. 

In fact, most RIAs and many nonisotopic immunoassays use a competitive binding format (see Fig. 2). In this approach, the analyte in the sample to be measured competes with a known amount of added analyte that has been labeled with an indicator that binds to the immobilized antibody. After reaction, the free analyte—analyte-indicator solution is washed away from the soHd phase. The analyte-indicator on the soHd phase or remaining in the wash solution is then used to quantify the amount of analyte present in the sample as measured against a control assay using only an analyte-indicator. This is done by quantifying the analyte-indicator using the method appropriate for the assay, for example, enzyme activity, fluorescence, radioactivity, etc. 

IQ. To determine the concentration of chloride ion, - a 5-mL aliquot of the methyl lithium solution is cautiously added to 25 ml of water and the resulting solution is acidified with concentrated sulfuric acid and then treated with 2-3 ml of ferric ammonium sulfate [Fe(NH4)( 04)2 12 H2O] indicator solution and 2-3 ml of benzyl alcohol. The resulting mixture is treated with 10.0 mL of standard aqueous 0.100 M silver nitrate solution and then titrated with standard aqueous 0.100 H potassium thiocyanate solution to a brownish-red endpoint. 

Indikator-folie, /. indicator foil, -losung, /. indicator solution. -papier, n. indicator paper. 

To approximately 20 ml of a 1 1 mixture of toluene (xylene) isopropyl alcohol, add 1 ml of oil-base mud and 75 to 100 ml of distilled water. Add 8 to 10 drops of phenolphthalein indicator solution and stir vigorously with a stirring rod (the use of a Hamilton Beach mixer is suggested). Titrate slowly with H SO, (N/10) until red (or pink) color disappears permanently from the mixture. Report the alkalinity as the number of ml of H SO (N/10) per ml of mud. Lime content may be calculated as... 

Calcium Chloride [25]. Calcium chloride estimation is based on calcium titration. To 20 ml of 1 1 mixture of toluene (xylene) isopropyl alcohol, add a 1-ml (or 0.1-ml, if calcium is high) sample of oil-base mud, while stirring. Dilute the mixture with 75 to 100 ml of distilled water. Add 2 ml of hardness buffer solution and 10 to 15 drops of hardness indicator solution. Titrate mixture with standard versenate solution until the color changes from wine-red to blue. If common standard versenate solution (1 ml = 20 g calcium ions) is used, then... 

Tests on a wide range of alloys at temperatures varying from 704 to 927°C have been made by Bernsen et al." to determine the temperature limits beyond which engineering materials carburise when held in contact with graphite. Table 7.27 lists the maximum penetrations of the carburised zones while nickel in general showed no visible evidence of carburisation the associated hardness measurements indicated solution of carbon even at 704°C. At this temperature the chromium-containing alloys showed little tendency to carburisation, but at 816°C carburisation leading to the formation of chromium carbide was rapid. 

The extent of pitting is estimated by a special microscopical technique, or by the attack on the substrate using an appropriate indicator. Thus in the case of steel 1,10-phenanthroline hydrochloride is added to the electrolyte (solution B) to detect the formation of Fe ions. Alternatively, the specimens can be removed from the corrosion test solution and placed in an indicator solution, i.e. solution C for zinc-base die castings and solution D for steels. 

Consider now two solute species Bi and B3, between which no direct experimental comparison by the colorimetric method is possible, because their useful concentration ranges just fail to overlap. We can find an intermediate indicator solute B2, whose useful range partly overlaps that of B, and partly overlaps that of B3. Using B2, a relation between Bi and B3 may thus be established indirectly. In dilute solution this relation will be a simple one. We do not know enough about concentrated solutions to be in a position to say whether a similar relation should be expected. In the experiments to be described, the first aim was to obtain an answer to this question. 

Chemicals. Indicator solutions ( 0.1 per cent, aq.). Bromophenol blue Congo red phenol red. 

Many of the indicator solutions are available from commercial suppliers already prepared for use. 

Mixed indicator solution. Mix two volumes of 0.1 per cent phenolphthalein solution and three volumes of 0.1 per cent thymol blue solution (both in ethanol). 

Note. In view of the varying stability of solutions of these indicators, and the possible variation in sharpness of the end point with the age of the solution, it is generally advisable (if the stability of the indicator solution is suspect), to dilute the solid indicator with 100-200 parts of potassium (or sodium) chloride, nitrate or sulphate (potassium nitrate is usually preferred) and grind the mixture well in a glass mortar. The resultant mixture is usually stable indefinitely if kept dry and in a tightly stoppered bottle. 

Aqueous solutions of murexide are unstable and must be prepared each day. The indicator solution may be prepared by suspending 0.5 g of the powdered dyestuff in water, shaking thoroughly, and allowing the undissolved portion to... 

The indicator solution is prepared by dissolving 0.2 g of the dyestuff in 15 mL of triethanolamine with the addition of 5 mL of absolute ethanol to reduce the viscosity the reagent is stable for several months. A 0.4 per cent solution of the pure dyestuff in methanol remains serviceable for at least a month. 

The indicator solution is prepared by dissolving 0.05 g of calmagite in 100 mL of water. It is stable for at least 12 months when stored in a polythene bottle out of sunlight. 

The indicator solution consists of a 0.5 per cent aqueous solution. 

The indicator solution consists of a 0.5 per cent solution in ethanol. Alternatively, a finely ground mixture (1 100) with potassium nitrate may be used. 

The indicator solution is a 1 per cent solution of the base in water. 

Procedure. Prepare an indicator solution by dissolving 0.5 g of fast sulphon black F in 100 mL of de-ionised water. 

Pipette 25 mL of the copper solution (0.01 M) into a conical flask, add 100 mL de-ionised water, 5 mL concentrated ammonia solution and 5 drops of the indicator solution. Titrate with standard EDTA solution (0.01 M) until the colour changes from purple to dark green. 

It should be noted that this method is only applicable to solutions containing up to 25 mg copper ions in 100 mL of water if the concentration of Cu2+ ions is too high, the intense blue colour of the copper(II) ammine complex masks the colour change at the end point. The indicator solution must be freshly prepared. 

Procedure. Prepare the indicator solution by dissolving 1 g variamine blue in 100 mL de-ionised water as already pointed out (Section 10.48), variamine blue acts as a redox indicator. 

Pipette 25 mL iron(III) solution (0.05M) into a conical flask and dilute to 100 mL with de-ionised water. Adjust the pH to 2-3 Congo red paper may be used — to the first perceptible colour change. Add 5 drops of the indicator solution, warm the contents of the flask to 40 °C, and titrate with standard (0.05M) EDTA solution until the initial blue colour of the solution turns grey just before the end point, and with the final drop of reagent changes to yellow. 

To determine the calcium in the calcium-magnesium mixture, pipette 25 mL of the solution into a 250 mL conical flask, add 25 mL of the buffer solution and check that the resulting solution has a pH of 9.5-10.0. Add 2mL of the Zn-EGTA solution and 2-3 drops of the indicator solution. Titrate slowly with the standard EGTA solution until the blue colour changes to orange-red. 

Notes. (1) Somewhat sharper end points may be obtained if the sample of water is first acidified with dilute hydrochloric acid, boiled for about a minute to drive off carbon dioxide, cooled, neutralised with sodium hydroxide solution, buffer and indicator solution added, and then titrated with EDTA as above. 

Pipette 25 mL of the solution to be analysed into a 250 mL conical flask and dilute to 100 mL with de-ionised water the original solution should be about 0.02M with respect to calcium and may contain barium to a concentration of up to 0.2M. Add 10 mL sodium hydroxide solution (1M) and check that the pH of the solution lies between 11 and 12 then add three drops of the indicator solution. Titrate with the standard CDTA solution until the pink colour changes to blue. 

Procedure. Place 10 mL of the solution containing the two metals (the concentration of neither of which should exceed 0.01 M) in a 600mL beaker fitted with a magnetic stirrer, and dilute to 100 mL with de-ionised water. Add 20 mL of standard (approx. 0.01 M) EDTA solution and add hexamine to adjust the pH to 5-6. Then add a few drops of the indicator solution (0.5 g xylenol orange dissolved in 100 mL of water) and titrate the excess EDTA with a standard lead nitrate solution (0.01 M), i.e. to the formation of a red-violet colour. 

To the resulting solution now add a further 20 mL portion of the standard EDTA solution, add nitric acid (1M) to adjust the pH to 1-2, and then boil the solution for 15 minutes. Cool, dilute to 400 mL by the addition of de-ionised water, add hexamine to bring the pH to 5-6, add more of the indicator solution, and titrate the excess EDTA with the standard lead nitrate solution. 

Procedure. Dissolve a weighed amount of ferro-manganese (about 0.40 g) in concentrated nitric acid and then add concentrated hydrochloric acid (or use a mixture of the two concentrated acids) prolonged boiling may be necessary. Evaporate to a small volume on a water bath. Dilute with water and filter directly into a 100 mL graduated flask, wash with distilled water and finally dilute to the mark. Pipette 25.0 mL of the solution into a 500 mL conical flask, add 5 mL of 10 per cent aqueous hydroxylammonium chloride solution, 10 mL of 20 per cent aqueous triethanolamine solution, 10-35 mL of concentrated ammonia solution, about 100 mL of water, and 6 drops of thymolphthalexone indicator solution. Titrate with standard 0.05M EDTA until the colour changes from blue to colourless (or a very pale pink). 

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