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Indicators standardisation

Several variations of the chemical method are in use. In the one described below, a freshly prepared Fehling s solution is standardised by titrating it directly against a standard solution of pure anhydrous glucose when the end-point is reached, I. e., when the cupric salt in the Fehling s solution is completely reduced to cuprous oxide, the supernatant solution becomes completely decolorised. Some difficulty is often experienced at first in determining the end-point of the reaction, but with practice accurate results can be obtained. The titrations should be performed in daylight whenever possible, unless a Special indicator is used (see under Methylene-blue, p. 463). [Pg.460]

It is essential to standardise the alcoholic potassium hydroxide solution immediately before use by titration with standard 0-5N or 0-25N hydrochloric or sulphuric acid using phenolphthalein as indicator. [Pg.393]

Two excellent methods (utilising acid-base indicators) are available for standardisation. The first is widely employed, but the second is more convenient, less time-consuming, and equally accurate. A third, back-titration, procedure is also available. [Pg.286]

B. Standardisation against sodium tetraborate. The advantages of sodium tetraborate decahydrate (borax) are (i) it has a large relative molecular mass, 381.44 (that of anhydrous sodium carbonate is 106.00) (ii) it is easily and economically purified by recrystallisation (iii) heating to constant weight is not required (iv) it is practically non-hygroscopic and (v) a sharp end point can be obtained with methyl red at room temperatures, since this indicator is not affected by the very weak boric acid. [Pg.288]

If the solution contains carbonate (Procedure A), methyl orange, methyl orange-ihdigo carmine, or bromophenol blue must be used in standardisation against hydrochloric acid of known molar concentration. Phenolphthalein or indicators with a similar pH range, which are affected by carbon dioxide, cannot... [Pg.292]

Procedure A with standard hydrochloric acid. Place the standardised (approx. 0.1 M) hydrochloric acid in the burette. Transfer 25 mL of the sodium hydroxide solution into a 250 mL conical flask with the aid of a pipette, dilute with a little water, add 1-2 drops of methyl orange or 3-4 drops of methyl orange-indigo carmine indicator, and titrate with the previously standardised hydrochloric acid. Repeat the titrations until duplicate determinations agree within 0.05 mL of each other. [Pg.293]

Sodium hydroxide. Prepare a solution of approximately 0.5M sodium hydroxide in methylcellosolve. This should be standardised by titration with potassium hydrogenphthalate using the mixed indicator given below. [Pg.307]

Solutions of EDTA of the following concentrations are suitable for most experimental work 0.1M, 0.05M, and 0.01 M. These contain respectively 37.224 g, 18.612g, and 3.7224 g of the dihydrate per litre of solution. As already indicated, the dry analytical grade salt cannot be regarded as a primary standard and the solution must be standardised this can be done by titration of nearly neutralised zinc chloride or zinc sulphate solution prepared from a known weight of zinc pellets, or by titration with a solution made from specially dried lead nitrate. [Pg.321]

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). [Pg.332]

Procedure. Prepare the CDTA solution (0.02M) by dissolving 6.880 g of the solid reagent in 50 mL of sodium hydroxide solution (1M) and making up to 1 L with de-ionised water the solution may be standardised against a standard calcium solution prepared from 2.00 g of calcium carbonate (see Section 10.61). The indicator is prepared by dissolving 0.5 g of the solid in 100 mL of water. [Pg.333]

Procedure. Prepare a manganese(II) sulphate solution (approx. 0.05M) by dissolving 11.15 g of the analytical-grade solid in 1 L of de-ionised water standardise the solution by titration with 0.05 M EDTA solution using solochrome black indicator after the addition of 0.25 g of hydroxylammonium chloride — see below. [Pg.334]

Standardisation. Pipette 10.0 mL of the sodium tetraphenylborate solution into a 250 mL beaker and add 90 mL water, 2.5 mL 0.1 M nitric acid, 1.0 mL iron(III) nitrate solution, and 10.0 mL sodium thiocyanate solution. Without delay stir the solution mechanically, then slowly add from a burette 10 drops of mercury(II) nitrate solution. Continue the titration by adding the mercury(II) nitrate solution at a rate of 1-2 drops per second until the colour of the indicator is temporarily discharged. Continue the titration more slowly, but maintain the rapid state of stirring. The end point is arbitrarily defined as the point when the indicator colour is discharged and fails to reappear for 1 minute. Perform at least three titrations, and calculate the mean volume of mercury(II) nitrate solution equivalent to 10.0 mL of the sodium tetraphenylborate solution. [Pg.359]

This method has the drawback that an excess of oxidising agent is always present at the end point. For work of the highest accuracy, the indicator blank may be determined and allowed for, or the error may be considerably reduced by performing the standardisation and determination under similar experimental conditions. [Pg.368]

Standardise the ammonium iron(II) sulphate solution against the 0.02/Vf potassium dichromate, using /V-phenylanthranilic add as indicator. Calculate the volume of the iron(II) solution which was oxidised by the dichromate originating from the chromium salt, and from this the percentage of chromium in the sample. [Pg.377]

Method A Standardisation with arsenic (III) oxide. Discussion. The most trustworthy method for standardising cerium(IV) sulphate solutions is with pure arsenic(III) oxide. The reaction between cerium(IV) sulphate solution and arsenic(III) oxide is very slow at the ambient temperature it is necessary to add a trace of osmium tetroxide as catalyst. The arsenic(III) oxide is dissolved in sodium hydroxide solution, the solution acidified with dilute sulphuric acid, and after adding 2 drops of an osmic acid solution prepared by dissolving 0.1 g osmium tetroxide in 40mL of 0.05M sulphuric acid, and the indicator (1-2 drops ferroin or 0.5 mL /V-phenylanthranilic acid), it is titrated with the cerium(IV) sulphate solution to the first sharp colour change orange-red to very pale blue or yellowish-green to purple respectively. [Pg.381]

Method B Standardisation with sodium oxalate. Standardisation may also be carried out with sodium oxalate in this case, an indirect procedure must be used as the redox indicators are themselves oxidised at the elevated temperatures which are necessary. The procedure, therefore, is to add an excess of the cerium(IV) solution, and then, after cooling, the excess is determined by... [Pg.381]

Weigh out accurately about 0.2 g sodium oxalate into a 250 mL conical flask and add 25-30 mL 1M sulphuric add. Heat the solution to about 60 °C and then add about 30 mL of the cerium(IV) solution to be standardised dropwise, adding the solution as rapidly as possible consistent with drop formation. Re-heat the solution to 60 °C, and then add a further 10 mL of the cerium(IV) solution. Allow to stand for three minutes, then cool and back-titrate the excess cerium(IV) with the iron(II) solution using ferroin as indicator. [Pg.382]

As already indicated, the first of these reactions is very useful for the generation of known amounts of iodine, and it also serves as the basis of a method for standardising solutions of acids (Section 10.110). [Pg.400]

The indicator electrode must be reversible to one or the other of the ions which is being precipitated. Thus in the titration of a potassium iodide solution with standard silver nitrate solution, the electrode must be either a silver electrode or a platinum electrode in the presence of a little iodine (best introduced by adding a little of a freshly prepared alcoholic solution of iodine), i.e. an iodine electrode (reversible to I-). The exercise recommended is the standardisation of silver nitrate solution with pure sodium chloride. [Pg.582]

Iron (III) solution, 0.05M. Dissolve about 12.0 g, accurately weighed, of ammonium iron(III) sulphate in water to which a little dilute sulphuric acid is added, and dilute the resulting solution to 500 mL in a graduated flask. Standardise the solution with standard EDTA using variamine blue B as indicator (Section 10.56). [Pg.725]

Potassium chloride (nitrate) bridge 583, 582 Potassium chromate as indicator, 343, 349 Potassium cyanoferrate(II) D. of, (ti) 384 Potassium cyanoferrate(III) D. of, (ti) 399 Potassium cyanonickelate(II) prepn., 328 Potassium dichromate solution analyses involving, 375 oxidising properties of, 375 internal indicators for, 377 preparation of, 0.02M, 375 redox indicators for, 377 standardisation of, by iron, (cm) 546, (ti) 376... [Pg.871]

Fig. 6. Comparison of the responses of two grasses of contrasted growth rate and morphology to five intensities of shoot impedance, (a) Lolium perenne b) Festuca ovina. Each curve records the mean progress of shoot expansion in five replicate plants subjected to standardised resistances (indicated on each curve as the force in newtons required for initial deflection of weighted windows). Plants were grown individually within a transparent cone, from which the shoots, in order to escape, must deflect windows of standard dimensions and angle of inclination. Fig. 6. Comparison of the responses of two grasses of contrasted growth rate and morphology to five intensities of shoot impedance, (a) Lolium perenne b) Festuca ovina. Each curve records the mean progress of shoot expansion in five replicate plants subjected to standardised resistances (indicated on each curve as the force in newtons required for initial deflection of weighted windows). Plants were grown individually within a transparent cone, from which the shoots, in order to escape, must deflect windows of standard dimensions and angle of inclination.
Sulphate has been determined in seawater by photometric titration with hydrochloric acid in dimethyl sulfoxide [223]. The sample (5 ml) is slowly added to dimethyl sulfoxide (230 ml) and titrated with 0.02 M hydrochloric acid (standardised against sulfate) with bromo-cresol green as indicator. Since borate, carbonate, and bicarbonate interfere, a separate determination of alkalinity is necessary. [Pg.105]

There is still a long way to go in the harmonisation of indices, applicability of new techniques and standardisation. These are essential steps in order to advance in the detection of the stressor effects by means of structural descriptors. However, even if these questions might be solved, the ability of structural descriptors to detect effects is limited. Many stressors occur in low concentrations, in acute episodes, or have side effects that are not reflected in the structure (composition, abundance) of the biofilm. In these cases where chronic effects would not occur, or are hidden, a finer scale of detection is required. [Pg.398]

The determination of neomycin by non-aqueous titration has been described by Penau et all2l. Neomycin base is allowed to react with standardised perchloric acid the excess acid is then back-titrated with potassium hydrogen phtha-late using crystal violet as indicator. To determine the neomycin content of the sulphate salt the same authors precipitated the sulphate with benzidine before reacting the neomycin with perchloric acid. The amount of benzidine required to precipitate the sulphate is calculated from the sulphate content which is itself determined by titration with sodium hydroxide. [Pg.428]

To compare between days and locations I standardised visitation rates for each species by calculating visits to each odour type as a proportion of mean visits to the blank stations by that species, on that night, and at that location. By making the data proportional I removed effects of differing population size and density, as well as variation between nights, for example in moon phase. These data were checked for normality and symmetry, and subsequently analysed with a two-tailed Wilcoxon signed ranks test (Zar 1999) to determine whether visitation rate differed from a value of one (indicating no difference between visitation rate to an odour source... [Pg.382]

Table 36.2 Standardised visit rates of rodents to odor stations (mean SEM), a value of one indicates no diiference between the visits to an odor station and to a blank. Shaded cells indicate a value significantly different to one (a = 0.05). [Pg.384]


See other pages where Indicators standardisation is mentioned: [Pg.360]    [Pg.1065]    [Pg.210]    [Pg.672]    [Pg.1376]    [Pg.992]    [Pg.294]    [Pg.295]    [Pg.305]    [Pg.307]    [Pg.308]    [Pg.325]    [Pg.359]    [Pg.384]    [Pg.769]    [Pg.855]    [Pg.859]    [Pg.873]    [Pg.360]    [Pg.1065]    [Pg.499]    [Pg.44]    [Pg.397]   


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Normalising (standardising) the indicators

Standardisation

Standardise

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