Reagent 1,5-diphenylcarbazide

Simultaneous determinations relying on a sandwich technique were demonstrated by the spectrophotometric determination of Cr(VI) and iron in waste waters [10]. To this end, the sample plug was inserted between two aliquots of the reagents 1,5-diphenylcarbazide and 1,10-phenanthroline. 

A more sensitive method is to employ 1,5-diphenylcarbazide CO(NHNHC6H5)2 in acid solution (ca 0.2M), chromates give a soluble violet compound with this reagent. 

Molybdenum(VI), vanadium(V), mercury, and iron interfere permanganates, if present, may be removed by boiling with a little ethanol. If the ratio of vanadium to chromium does not exceed 10 1, nearly correct results may be obtained by allowing the solution to stand for 10-15 minutes after the addition of the reagent, since the vanadium-diphenylcarbazide colour fades fairly rapidly. Vanadate can be separated from chromate by adding oxine to the solution and extracting at a pH of about 4 with chloroform chromate remains in the aqueous solution. Vanadium as well as iron can be precipitated in acid solution with cupferron and thus separated from chromium (III). 

Procedure. Prepare a 0.25 per cent solution of diphenylcarbazide in 50 per cent acetone as required. The test solution may contain from 0.2 to 0.5 part per million of chromate. To about 15 mL of this solution add sufficient 3M sulphuric acid to make the concentration about 0.1M when subsequently diluted to 25 mL, add 1 mL of the diphenylcarbazide reagent and make up to 25 mL with water. Match the colour produced against standards prepared from 0.0002M potassium dichromate solution. A green filter having the transmission maximum at about 540 nm may be used. 

Diphenylcarbazide as adsorption indicator, 358 as colorimetric reagent, 687 Diphenylthiocarbazone see Dithizone Direct reading emission spectrometer 775 Dispensers (liquid) 84 Displacement titrations 278 borate ion with a strong acid, 278 carbonate ion with a strong acid, 278 choice of indicators for, 279, 280 Dissociation (ionisation) constant 23, 31 calculations involving, 34 D. of for a complex ion, (v) 602 for an indicator, (s) 718 of polyprotic acids, 33 values for acids and bases in water, (T) 832 true or thermodynamic, 23 Distribution coefficient 162, 195 and per cent extraction, 165 Distribution ratio 162 Dithiol 693, 695, 697 Dithizone 171, 178... 

Reagent iodine vapour phosphomolybdic acid fluorescein/bromine sulphuric acid ninhydrin or isotin 2,4 -dinitropheny lhy drazine H2S water, diphenylcarbazide or... 

Miller and Zittef have used 1,5-diphenylcarbazide (0.25% solution in acetone) for the spectrophotometric determination of technetiiun. 1 to 15 /ig of technetium in 10 ml solution can be ascertained by measuring the extinction at 520 nm of the Tc (IV) complex in 1.5 M sulfuric acid. The development of the most intense color takes about 35 min the reduction of pertechnetate to Tc (IV) is effected by the reagent itself before complexation occurs. The molar extinction coefficient of the complex at 520 nm is 48,600. The relative standard deviation is 2%. Fe ", Ce ", and CrOj" clearly disturb measurements, VO , MoOj ,... 

Trace polonium is extracted from aqueous acetate solution by 8-hy-droxyquinoline in chloroform, probably forming a 1 1 compound this sublimes at 140°C (81). The thionalide complex appears to have 2 molecules of ligand to each polonium atom volatile complexes with thiourea, thio-semicarbazide, diphenylcarbazide, and analogous reagents have also been reported (81). 

The eluted Cr(VI) solution was acidified with HC1 and treated with a solution of 1,5-diphenylcarbazide, a reagent that forms a... 

I, 5-diphenylcarbazide and chromium(III). P. Cazeneuve (1900), and F. Feigl and F. L. Lederer (1925) later used the procedure for certain separations.5 However, the most pregnant discovery was made by Helmuth Fischer (1925) when he pioneered the analytical applications of dithizone, PhNHNHCSN==NPh. Here both the reagent and its metal complexes are intensely coloured, soluble in organic solvents but insoluble in water. Only a small number of metals react and the procedures can readily be made highly selective.7 8... 

Place a drop of the test solution in mineral acid on a spot plate, introduce a drop of saturated bromine water followed by 2-3 drops 2m potassium hydroxide (the solution must be alkaline to litmus). Mix thoroughly, add a crystal of phenol, then a drop of the diphenylcarbazide reagent, and finally M sulphuric acid dropwise until the red colour (from the reaction between diphenylcarbazide and alkali) disappears. A blue-violet colouration is obtained. 

Alternatively, mix a drop of the acidified test solution on a spot plate with 2 drops 01m potassium peroxodisulphate solution and 1 drop 01m silver nitrate solution, and allow to stand for 2-3 minutes. Add a drop of the diphenylcarbazide reagent. A violet or red colour is formed. 

The reagent consists of a 1 per cent solution of diphenylcarbazide in alcohol. 

The reagent is prepared by dissolving 0 2 g diphenylcarbazide in 10 ml glacial acetic acid and diluting to 100 ml with ethanol. 

The spot-test technique is as follows. Into the tube of Fig. 11.57 place a few milligrams of the solid sample (or evaporate a drop or two of the test solution in it), add a small quantity of powdered potassium dichromate and a drop of concentrated sulphuric acid. Place a column about 1 mm long of a 1 per cent solution of diphenylcarbazide in alcohol into the capillary of the stopper and heat the apparatus for a few minutes. The chromyl chloride evolved causes the reagent to assume a violet colour. 

Place a drop of the test solution in a micro crucible and add a drop of the reagent. Warm rapidly over a micro burner and allow to cool. A violet colouration appears. Very pale colourations may be intensified by adding a drop of 1 per cent alcoholic diphenylcarbazide solution when a deep-violet colour, due to an oxidation product of the diphenylcarbazide, is obtained. 

Diphenylcarbazide reagent The solution is acidified with dilute sulphuric acid or with dilute acetic acid, and 1-2 ml of the reagent added. A deep-red colouration is produced. With small quantities of chromates, the solution is coloured violet. 

Heat with sodium carbonate and potassium nitrate This test may be carried out in a loop of platinum wire or upon platinum foil or upon a piece of broken porcelain. If chromium is present, a yellow melt is produced. This should be dissolved in water, acidified with dilute acetic acid, and (a) silver nitrate solution added, when brownish-red silver chromate is precipitated, (6) lead acetate solution added, when yellow lead chromate is precipitated, or (c) 1-2 ml diphenylcarbazide reagent added, when a deep-red colouration is produced. 

An extremely selective reagent for chromium(VI) is 1,5-diphenylcarbazide which, in acidic solution, forms an analytically useful inner complex with dichromate. Like the metal-PAR complexes, it is red-purple colored and, thus, may be photometrically detected at 520 nm. The chromate separation is performed - as already mentioned — by means of anion exchange. 

Reagents related to dithizone are 1,5-diphenylcarbazide (formula 17.1), a reagent for Cr(VI) and Os, and diphenylcarbazone which is used, inter alia, for determining mercury. To the same family of reagents belong 1,5-diphenylthiosemicarbazide (formula 42.1) and 2,4-diphenylthiosemicarbazide, which are valuable spectrophotometric reagents for Ru, Re, Se, and Te. The application of thiosemicarbazones and semicarbazones in spectrophotometry has been reviewed [94,95]. 

Diphenylcarbazide, 0.2% solution in acetone. Dissolve 0.2 g of the reagent in 100 ml of acetone containing 1 ml of H2SO4 (1+9). Keep the solution in an amber-glass bottle. 

Many other organic reagents have been applied for spectrophotometric determination of gold, e.g. dithizone [64], diphenylcarbazide (eX= 4.2-10 at 560 nm) [65], PAR [66], TAR... 

Various other organic reagents have been proposed for determining Rh, viz. nitroso-R salt [57,58], 1,5-diphenylcarbazide [59], Chrome Azurol S (in the presence of CP) (e = 6.2-10" ) [60], and Chrompyrazole I in the presence of SnCl2 [61]. Rhodanine derivatives have been used for determination of Rh in the presence of Pd [62] and heavy metals [63]. 

Among other organic reagents used for determining Ir, are a-benzilmonoxime [82-84] and 1,5-diphenylcarbazide [59]. Diphenylamine sulphonate has been used for determination of various nitrite-chloride complexes of iridium [85]. 

Diphenylcarbazide, a well-known reagent for Cr(VI), has been applied for the spectrophotometric determination of Os [79]. Diphenylcarbazide (in ethanol) reacts with OSO4 (in CHCI3) to form a blue-green complex having max 560 nm. A freshly prepared solution of 1,5-diphenylcarbazide does not absorb between 400 and 700 nm. The molar absorptivity of the osmium complex in CHCI3 is 3. MO. The sensitivity has been increased as a result of certain modifications [80,81]. Now, osmium tetroxide is made to react with... 

In its reversed mode, FIA is fully adaptable to Industrial process control [49-51], and to studies of the speciation of various elements In waters [102]. One of the most promising developments in the latter area is the speciation of chromium by means of the configuration depicted in Fig. 6.20. This uses a combined giass-calomel microelectrode incorprorated in the sample stream prior to the simultaneous injection of the reagents (Ce and 1,5-diphenylcarbazide for Cr3+ and Cr(VI). The data obtained for the concentration of these two species, together with the sample pH and the constants corresponding to the equilibria in which both oxidation states are involved, allow the calculation of the concentration of up to nine different chromium species aquo complexes and hydroxylated forms of Cr(III) and ionic, molecular and dimeric forms of Cr(VI) [103]. 

Locating reagents (a) rubeanic acid/salicylaldoxime/alizarin (RSA) (b) diphenylcarbazide (c) sodium pentacyanoammine ferrate(II)/rubeanic acid (PCFR). 

Diphenylcarbazide reagent (C(,Hs NH NH CO NH NH C H ) (0.2%) The magnesium salt solution is treated with sodium hydroxide solution - a precipitate of magnesium hydroxide will be formed - then with a few drops of the diphenylcarbazide reagent and the solution filtered. On washing the precipitate with hot water, it will be seen to have acquired a violet-red colour due to the formation of a complex salt or an adsorption complex. Metals of Groups II and III interfere and should therefore be absent. 

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