Methyl purple

The hoses are disconnected and replaced with a beaker of indicator and a rubber bulb (Figure b). For an indicator, we use slightly alkaline methyl purple, which is green above pH 5.4 and purple below pH 4.8. When 1 mL of water is squirted from the rubber bulb into the flask, a vacuum is created and indicator solution is drawn up into the flask, making a fascinating fountain (Color Plate 1). 

Direct electron transfer from P-430 to exogenous acceptors (methyl or benzyl viologen, safranine T, etc.) has been demonstrated the reaction also occurs with ferredoxin [9]. Many other acceptors can accept electrons from PS I but their site of reaction is not known. Recently, methyl purple has been introduced as a specific PS I acceptor with useful spectroscopic properties [33]. 

Accurately weigh 1-2 g of sample and make up a sample solution of 100 ml. Mix 20 ml of the sample solution with 2 drops of methyl purple indicator and 50 ml of freshly prepared 1 Ig 1 periodic acid solution. Shake well. 

Add 100 ml of distilled water and 3 drops of methyl purple indicator to the sample solution and the blank. Titrate with 0.1 N NaOH to neutral pH. 

Bromcresol green can be used in a manner similar to methyl red. Its transition range is pH 3.8 to 5.4, with a color change from blue through pale green to yellow (see Experiment 7). Similarly, methyl purple can be used (see Experiment 19). 

Note that between the first and second end points, a gradual decrease in pH due to the HC03"/C02 buffer system will occur. This will give a poor visual end point, unless the buffer couple is destroyed. In practice, the visual titration used for standardization is continued until the methyl purple end point is reached, at which time the solution is gently boiled to remove the CO2, leaving only the remaining HCOs", which is then titrated to completion (see Chapter 8 for a more detailed discussion). 

Provided. 0.2% phenolphthalein in 95% ethanol, 0.1% methyl purple in water, primary standard Na2C03, standard pH 7 buffer. 

The acid phase was divided into several portions that were used to make the following measurements. The total acidity (reported as percent sulfuric acid) was determined by titration with a standard sodium hydroxide solution using a methyl purple indicator. Total sulfuric acid was determined in a second sample in a similar manner after the nitric acid and lower oxides of nitrogen were expelled by evaporation on a steam bath. Lower oxides of nitrogen were determined by a redox method. Total nitric acid was determined by difference. 

Other Names Heisher s Methyl purple indicator... 

Graan, T. Ort, D. R. Prince, R. C. Methyl purple, an exceptionally sensitive monitor of chloroplast photosystem I turnover physical properties and synthesis. Anal. Biochem. 1985,144,193-198. 

Transfer a 25 ml aliquot of the standard ammonium chloride solution (1 ml = 10 pg N) into the distillation tube of the nitrogen apparatus and 10 ml boric acid solution (1 %) and 2 drops methyl purple (bromo-cresol green/methyl red) solution (0.1 %) into the receiving flask the tip of the outlet should be just above the solution in the receiving flask. 

Quantitatively transfer the absorber contents to a 500-mL Erlenmeyer flask, using ion-free water for rinsing. Add 2 drops of Fleisher s methyl purple indicator solution to this solution and titrate to a faint green end point with 0.03 M NaOH solution (Note 12). Add 1 mL more of the 0.03 M NaOH solution to the solution and reduce the volume to 2 to 3 mL by evaporation on a hot plate in sulfate-free environment. (Warning—see Note 11) DO NOT BOIL DRY. Cool the solution to room temperature and measure its volume in a 10-mL graduate (Note 12). Adjust the volume to 3.0 mL by adding ion-free water. 

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