Indigo-carmine solution

Calcium Acetate Dissolve 1.0 g in 10 ml DW, add 5 mg NaCl 0.05 ml indigo-carmine solution and with stirring 10 ml ofN2-free H2S04. The blue colour remains for at least 10 minutes. 

Indigo-Carmine Solution To a mixture of 10 ml of HC1 and 990 ml of a 20% w/v soln. of N2-free H2S04 in DW, add sufficient indigo-carmine (about 0.2 g) to produce a solution that complies with the following test Add 10 ml to a soln. of 1.0 mg of KNOs in 10 ml DW, rapidly add 20 ml HjSC and heat to boiling. The blue colour is just discharged in 1 minute. 

Also by oxidising the carmine solution with permanganate for the determination of the mdigotin, many artificial organic dyes may be detected thus, pure indigo carmine solution remains yellow, whereas it may be bluish, violet, grey or reddish in presence of artificial organic dyes. 

The use of an external indicator is somewhat tedious, but the titration can be simplified by using indigo carmine. This substance is readily decolorized by the available chlorine. A measured volume of arsenious oxide solution such as 25 ml, together with a little hydrochloric acid, are placed in a titration flask and a few drops of indigo carmine solution are added. The hypochlorite is then run in from a burette until the blue colour changes to a yellowish tinge. 

Weigh out accurately about 0 2 g of the substance, and transfer to a 200-ml conical flask. Dissolve it in a mixture of 10 ml of 95 per cent ethanol and 15 ml of glacial acetic acid. Add 4 g of anhydrous sodium carbonate and 25 ml of 10 per cent sodium potassium tartrate solution. Titrate with O IN titanous chloride, using 3 drops of 0 1 per cent indigo carmine solution as indicator. A sharp end-point is obtained, the blue dye being changed to the colourless leuco base by the addition of 1 drop of the titanous chloride solution in excess. Phenosafranine is also a suit-... 

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. 

Titration of 25.00 mL of the carbonate solution with 0.1060M HC1, using methyl orange-indigo carmine as indicator. 

Procedure B. The experimental details for the preparation of the initial solution are similar to those given under Procedure A. Titrate 25 or 50 mL of the cold solution with standard 0.1M hydrochloric acid and methyl orange, methyl orange-indigo carmine, or bromophenol blue as indicator. Titrate another 25 or 50 mL of the cold solution, diluted with an equal volume of water, slowly with the standard acid using phenolphthalein or, better, the thymol-blue cresol red mixed indicator in the latter case, the colour at the end point is rose. Calculate the result as described in the Discussion above. 

The two methods available for this determination are modifications of those described in Section 10.32 for hydroxide/carbonate mixtures. In the first procedure, which is particularly valuable when the sample contains relatively large amounts of carbonate and small amounts of hydrogencarbonate, the total alkali is first determined in one portion of the solution by titration with standard 0.1M hydrochloric acid using methyl orange, methyl orange-indigo carmine, or bromophenol blue as indicator ... 

In the direct method, a solution of the ammonium salt is treated with a solution of a strong base (e.g. sodium hydroxide) and the mixture distilled. Ammonia is quantitatively expelled, and is absorbed in an excess of standard acid. The excess of acid is back-titrated in the presence of methyl red (or methyl orange, methyl orange-indigo carmine, bromophenol blue, or bromocresol green). Each millilitre of 1M monoprotic acid consumed in the reaction is equivalent to 0.017032 g NH3 ... 

In the indirect method, the ammonium salt (other than the carbonate or bicarbonate) is boiled with a known excess of standard sodium hydroxide solution. The boiling is continued until no more ammonia escapes with the steam. The excess of sodium hydroxide is titrated with standard acid, using methyl red (or methyl orange-indigo carmine) as indicator. 

The mineralization of 0.2 mM Indigo Carmine was conducted in a batch photo reactor (0.5 L) in the presence of 8W UVC light and 10 mM H2O2 at different initial solution pHs and 30 C, as described in our previous study [4]. The total organic carbon (TOC) of the... 

Fig. 2. displays the TOC removal of 0.2 mM Indigo Carmine as a fimction of time under different initial solution pHs in the presence of 10 mM H2O2, 1.0 g Fe-B/L, and 8W UVC. As the initial solution pH increases from 3.0 to 7.0, the mineralization kinetics becomes slower, indicating that the Fe-B nanocompsoite showed a decreased photo catalytic activity. For example, the difference between the TOC removal at initial solution pH of 3.0 and 7.0 is about 25 /o, which agrees well with previous studies [1-3]. 

However, it should be noticed that even we started the reaction at a neutral solution pH of 7.0, the TOC removal of 0.2 mM Indigo Carmine can also be achieved over 60% after 120 minutes reaction, implying that the Fe-B nanocomposite exhibited a reasonable good activity when the initial solution pH is neutral. The result also reveals that pre-adjustment of initial solution pH may not be necessary, and makes it feasible for the Fe-B nanocomposite to be applied to real industrial application for wastewater treatment. 

In order to explain the results shown in Fig. 2., the solution pH as a function of time was measured by a pH meter, and the results are displayed in Fig. 3. As can be seen from the data in the figure, when the initial solution pH is over 3.0, as reaction time increases, the solution pH decreases very fast to around 3.5 within 10 minutes, then reaches a lowest value of around 3.2 at 60 minutes, followed by a slight increase. What causes this interesting phenomenon We believed that the rapid decrease in solution pH is due to the fact that acidic intermediates are formed during the mineralization of 0.2 mM Indigo Carmine. Because of its complicated molecular structure, theoretically, it caimot be oxidized completely into CO2 and H2O in one step. 

Fig. 3. Solution pH as a function of time during mineralization of 0.2 mM Indigo Carmine Carmine in the presence of 10 mM H2O2, 1.0 g Fe-B/L, 8WUVC, and at 30 °C.

Sulphuric Acid Carefully add 5.0 ml to a mixture of 5 ml DW and 0.5 ml indigo carmine soln. and allow to stand for 1 minute. The colour of the solution is discharged. 

Indigo carmine is fixed by wool in an acid hath and may then lie removed from the wool by boiling this with dilute sodium carbonate solution. The solution thus obtained gives the following reactions with sulphuric acid, a blue coloration with jxitash it decolorises somewhat, with. stannous chloride, it becomes decolorised m the hot (the colour jcHppcars on addition of ferric chloride) by nitric a id or chlorine water it is ilecohuised (the colour cannot be restored in any way). 

Artificial Organic Dyes.—Indigo carmine may be adulterated with artificial organic dyes, especially aniline blue. If silk is dyed with an acidified solution of the carmine and then washed and boiled with water, the fibre will become colourless if the carmine is pure, but remains blue if aniline blue is present. 

The great oxidation power of electro-Fenton with BDD has also been confirmed in the comparative treatment of acidic aqueous solutions containing up to 0.9 g dm-3 of the dye Indigo Carmine by electro-Fenton and photoelectro-Fenton using BDD/02 and Pt/02 cells (Flox et al. 2006). The application of both methods... 

Acidify a portion of the sample with dilute sulphuric acid, and add 1 ml of a 1% solution of indigo carmine. A deep blue colour is given by chlorates. 

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