Bromocresol green, acid-base

The most common acid-base indicators are either azo dyes for example, methyl orange and methyl red nitrophenols phthaleins such as phenol-phthalein or thymolphthalein or sulfonephthaleins like bromophenol blue or bromocresol green. Acid-base indicators are available that cover visual transitions usually expressed in intervals of 2 pH units ranging from pH 0.0 to 2.0 in small increments up to pH 12.0-14.0. 

It is clear that neither thymolphthalein nor phenolphthalein can be employed in the titration of 0.1 M aqueous ammonia. The equivalence point is at pH 5.3, and it is necessary to use an indicator with a pH range on the slightly acid side (3-6.5), such as methyl orange, methyl red, bromophenol blue, or bromocresol green. The last-named indicators may be utilised for the titration of all weak bases (Kb> 5 x 10-6) with strong acids. 

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 ... 

A dual-transducer approach based on sol-gel optical sensors was recently reported to measure acid and salt concentrations in concentrated aqueous and HC1 solutions57. The acid sensors containing bromocresol purple, neutral red, and bromocresol green indicators were obtained by the immobilization of indicators in sol-gel derived films. The salt-HCl solution was flowed through the sensor cell58. 

The identity of methanesulphonic acid may be determined by tic on cellulose plates, Merck no. 5728, with ethanol/ water/conc. ammonia 80 16 4 (v/v/v) as a mobile phase. Detection is achieved by spraying with acid-base indicators, e.g. bromocresol green or similar species. Rf of methanesulphonic acid is 0.5 (that of bromocriptine base = 0.9). 

Would the indicator bromocresol green, with a transition range of pH 3.8—5.4, ever be useful in the titration of a weak acid with a strong base ... 

Using 2NpOH and 2-naphthol-3,6-disulfonate [121] as excited-state proton emitters, a transient high proton concentration is achieved on the membrane surface. With bromocresol green dye adsorbed on the membrane serving as a pH indicator, it has been found that the protons first react with the acidic ionized moieties on the surface and then reach the strongest base on the surface by rapid exchange. 

Alkalinity co - I ICO, Acid-base titration Titrating with standardized 0.01 M H2S04 using phenolphthalein as indicator until the pink color disappears at about pH 8.3 titration of the same sample is then continued until the end point is reached at pH 4.5 using a bromocresol green-methyl red mixed indicator (total alkalinity) Applicable to natural and waste water. Concentrations of bicarbonate, carbonate, and hydroxide can be calculated. The titration end points can be measured potentiometrically 50,51,67-69... 

A 1 to 1.5 A/ solution of methylamine in benzene is prepared by leading methylamine (from a lecture bottle) through 100 mL of dry benzene during about 30 min. The actual concentration of the amine is determined by acid-base titration, using dilute hydrochloric acid and bromocresol green as indicator. 

Figures 14-5 and 14-6 show that the choice of indicator is more limited for the titration of a weak acid than for the titration of a strong acid. For example. Figure 14-5 illustrates that bromocresol green is totally unsuited for titration of 0.1000 M acetic acid. Bromothymol blue does not work either because its full color change occurs over a range of titrant volume from about 47 mL to 50 mL of 0.1000 M base. An indicator exhibiting a color change in the basic region, such as phenolphthalein, however, should provide a sharp end point with a minimal titration error.

Although production of each carbonate ion uses up two hydroxide ions, the uptake of carbon dioxide by a solution of base does not necessarily alter its combining capacity for hydronium ions. Thus, at the end point of a titration that requires an acid-range indicator (such as bromocresol green), each carbonate ion produced from sodium or potassium hydroxide will have reacted with two hydronium ions of the acid (see Figure 16-1) ... 

The indicators were obtained from Kodak Laboratory Chemicals, Aldrich Chemical Company, and J.T. Baker and were used without further purification. The indicators employed in the majority of the titrations were bromocresol green and bromothymol blue each of which exhibits two acid-base transitions at Pka = -3.7, +4.6, and -1.5, +6.8, respectively(20, 22, 26) The medium for the titration and electrophoretic mobility experiments was benzene (Burdick and Jackson Laboratories) having a water content of less than 0.03 percent. The base used as titrant was n-butylamine, Baker analyzed reagent grade. 

Table 16.4 shows the pH range of selected acid-base Indicators. Use this table to help you decide the colour of phenolphthalein and bromocresol green at a pH of... 

Choice of indicators from Table 16.4 for a weak base-strong acid titration are bromocresol green and methyl red. The remaining indicators begin to change colour before or after the pH at the equivalence point (-pH 4-8). 

Acids and bases Bromocresol green, bromocresol purple, bromophenol blue, methyl red. All 0-5% in 50% aqueous ethanol. [3, 24] [2, 25]... 

Spraying with a 0.01-1% aqueous or aqueous alcohol solution of an acid-base indicator (e.g., bromocresol green, bromothymol blue, bromophenol blue, methyl red, malachite green) can detect acid or basic compounds on the layer based on a change in color at the location of the zones and knowledge of the pH transition range of the indicator. 

The acceptor stream, where the released SO2 is collected, is usually a solution containing an acid-base indicator. The SO2 gas released from the donor diffuses through the membrane and is dissolved into the acceptor solution. Which acceptor is used (iodine, bromocresol green, malachite green, etc.) in sulfite determination depends on the detection system concerned (spectrophotometry, fluorometry, amperometry, etc.) (Figures 8.1 and 8.2). 

The titration of aminophylline, which is the salt of theophylline (the acid) and ethylenediamine (the base), is performed in water with hydrochloric acid in the presence of bromocresol green (3.8[Pg.177]

The base is assayed by solution in excess of standard acid and back-titration of the excess with bromocresol green as indicator, 1 ml 0-01N = 0-01992 g C23H30O4N2. It can also be determined by non-aqueous titration (p. 792). 

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