Phenol red solution

Procedure Weigh and powder 20 tablets. Accurately weigh a quantity of the powder equivalent to about 0.5 g of aspirin, add 30.0 ml of 0.5 N sodium hydroxide boil gently for 10 minutes and titrate with 0.5 N hydrochloric acid using phenol red solution as an indicator. Repeat the operation without the substance being examined, the difference between the titrations represents the amount of 0.5 N sodium hydroxide required by the aspirin. Each ml of 0.5 N sodium hydroxide is equivalent to 0.04504 g of... 

Dilute stocks to a working concentration in an injection buffer. A lx Danieau buffer is often used, but a 1% phenol red solution provides the advantage of visual confirmation of which embryos have been injected. 

In the procedure of the Europaeisches Arzneibuch [16], 0.2 g of benzoic acid is dissolved in 20 mL of 96% ethanol, and titrated with 0.1 M NaOH. Using phenol red solution as the indicator, the endpoint is indicated when the color changes from yellow to violet. 

According to the British Pharmacopoeia 2002, the European and Indian Pharmacopoeias, and the Pharmacopoeia of the People s Republic of China, the assay for mefenamic acid is performed by a titration method. About 0.200 g of the substance to be assayed is dissolved with the aid of ultrasound in 100 mL of warm ethanol that has been previously neutralized to the phenol red endpoint. About 0.1 mL of phenol red solution is added and titrated with 0.1 M sodium hydroxide. Each milliliter of 0.1 M NaOH is equivalent to 24.13 mg of mefenamic acid [2, 5-7],... 

Place an approximately neutral sample solution ( 12 ml), eontaining not more than 100 pg of Bf, in a 25-ml standard flask, add 4 ml of the borate buffer, 1 ml of the hypochlorite solution, and shake for 2 min. Add 1.0 ml of the Phenol Red solution, stir well, and let the solution stand for 4 min. Add 1.2 ml of the arsenite solution and 4 ml of the acetate buffer, and dilute to the mark with water. Measure the absorbance of the solution at 580 nm against a blank solution. 

Phenol red Add 129mg NaHCOj (Sigma) to 7.4mL super quality H O (Milli-pore) and add 2.6 ml of 0.5% phenol red solution (Sigma). 

Dissolve 0 5 g of theobromine and sodium salicylate in 100 ml of hot water, add 15 ml of 0-1N sulphuric acid and boil to remove carbon dioxide. C ool to 40, add 15 ml of phenol red solution and a measured quantity of O IN sodium hydroxide until the mixture is alkaline (2 to 3 ml required). Titrate with O IN sulphuric acid until the colour of the indicator changes to lemon yellow. The amount of 0 1 N sodium hydroxide deducted from the total 0-1N acid is a measure of the alkalinity. To this solution add 20 ml of O IN silver nitrate and titrate the liberated nitric acid with O IN sodium hydroxide to a deep red-violet colour. 1 ml O IN 001802 g theobromine. The approach of the endpoint is indicated by incipient precipitation of silver oxide. 

Note. Some substituted phenols, particularly nitrophenols, are sufficiently acidic to liberate CO, from Na,CO,. Nitrophenols, however, all give yellow or red solutions with NajCOj. 

Ltease test. The enzyme uretwe hydrolyses urea to ammonium carbonate (p. 519). The reaction is sp ific and is frequently used for solu tions of urea to which the biuret test cannot be applied. Add about 5 drops of phenohred to o 2 g. of urea dissolved in 5 ml. of water. To this yellow solution, add 0 2 g. of jack bean meal suspended in 2 ml. of water containing. also 5 drops of phenol-red. The colour changes to red as the solution becomes alkaline. 

The principle of this test is as follows The liquid suspected of containing urea is treated with dilute acid or alkali until its pH is about 7. A solution of the enzyme is also made and its pH adjusted to 7. The two solutions are mixed and the resulting conversion of urea to ammonium carbonate causes the pH of the solution to rise to over 8 this change is noted by the use of a suitable indicator, phenol-red being the one usually employed. Proteins do not interfere with the test, but the reaction is inhibited by traces of heavy metals. 

Place about 0 2 g. of jack-bean meal in a test-tube, add 2 ml. of water and about 5 drops of phenol-red. Mix thoroughly and allow the faintly yellow solution to stand while the urea solution is being made up. 

Phenolsulphonephthalein (phenol red). Mix 10 g. of o-sulpho-benzoic anhydride (Section VIII,9), 14 g. of pure phenol and 10 g. of freshly fused zinc chloride in a small conical flask. Place a glass rod in the flask and heat gently over a flame to melt the phenol. Then heat the flask containing the well-stirred mixture in an oil bath at 135-140° for 4 hours. Stir from time to time, but more frequently during the first hour if the mixture froths unduly, remove the flask from the bath, cool and then resume the heating. When the reaction is complete, add 50 ml. of water, allow the water to boil and stir to disintegrate the product. Filter the crude dye with suction and wash it well with hot water. Dissolve the residue in the minimum volume of warm (60°) 20 per cent, sodium hydroxide solution, filter, and just acidify the filtrate with warm dilute hydrochloric acid (1 1). Filter the warm solution, wash with water, and dry upon filter paper. The yield of phenol red (a brilliant red powder) is 11 g. 

The pH is measured colorimetricaHy with phenol red indicator. High FAC causes lower pH rea dings due to bleaching of the indicator and resultant HCl formation. The pH of pool water is readily controlled with inexpensive chemicals. Hydrochloric acid solution or sodium bisulfate lower it, whereas sodium carbonate raises it. Since acid addition neutralizes a portion of the alkalinity, this must be replenished if the alkalinity drops below the minimum. By contrast, pH adjustment with carbon dioxide does not affect alkalinity. 

Phenol red is an indicator with a pffa of 7.4. It is yellow in acid solution and red in alkaline. 

Chemicals. Indicator solutions ( 0.1 per cent, aq.). Bromophenol blue Congo red phenol red. 

Carefully scrape the separated bromophenol blue spots on to a sheet of clean smooth-surfaced paper using a narrow spatula (this is easier if two grooves are made down to the glass on either side of the spots). Pour the blue powder into a small centrifuge tube, add 2 mL of ethanol, 5 drops of 0.880 ammonia solution, and stir briskly until the dye is completely extracted. Centrifuge and remove the supernatant blue solution from the residual white powder. Repeat this procedure with the separated Congo red and phenol red spots . 

Sulphonphthaleins. These indicators are usually supplied in the acid form. They are rendered water-soluble by adding sufficient sodium hydroxide to neutralise the sulphonic acid group. One gram of the indicator is triturated in a clean glass mortar with the appropriate quantity of 0.1 M sodium hydroxide solution, and then diluted with water to 1 L. The following volumes of 0.1 M sodium hydroxide are required for 1 g of the indicators bromophenol blue, 15.0 mL bromocresol green, 14.4 mL bromocresol purple, 18.6 mL chlorophenol red, 23.6 mL bromothymol blue, 16.0 mL phenol red, 28.4 mL thymol blue, 21.5 mL cresol red, 26.2 mL metacresol purple, 26.2 mL. 

With 0.01M solutions, the ideal pH range is still further limited to 5.5-8.5 such indicators as methyl red, bromothymol blue, or phenol red will be suitable. The titration error for methyl orange will be 1-2 per cent. 

Pipette 25 mL of an aluminium ion solution (approximately 0.01 M) into a conical flask and from a burette add a slight excess of 0.01 M EDTA solution adjust the pH to between 7 and 8 by the addition of ammonia solution (test drops on phenol red paper or use a pH meter). Boil the solution for a few minutes to ensure complete complexation of the aluminium cool to room temperature and adjust the pH to 7-8. Add 50 mg of solochrome black/potassium nitrate mixture [see Section 10.50(C)] and titrate rapidly with standard 0.01 M zinc sulphate solution until the colour changes from blue to wine red. 

To a solution of 71.9 g (0.276 mol) of chlorotriisopropoxytitanium in 500 ntL of anhyd toluene are added 77.9 g (0.828 mol) of phenol. From the deep red solution, most of the i-PrOH and the solvent is removed by distillation through a 10-cm Vigretlx column. The residue is distilled in a Kugelrohr at 250 C bath temperature at 0.001 Torr to give an oil which crystallizes upon cooling yield 95.8 g (96%). A 0.26M slock solution in THF can be kept as described above. 

Gravimetric and volumetric methods are practicable for the quantitative determination of the a-sulfo fatty acid esters. Using gravimetric methods the surfactant is precipitated with p-toluidine or barium chloride [105]. The volumetric determination method is two-phase titration. In this technique different titrants and indicators are used. For the analysis of a-sulfo fatty acid esters the quaternary ammonium surfactant hyamine 1622 (p,f-octylphenoxyethyldimethyl-ammonium chloride) is used as the titrant [106]. The indicator depends on the pH value of the titration solution. Titration with a phenol red indicator is carried out at a pH of 9, methylene blue is used in acid medium [106], and a mixed indicator of a cationic (dimidium bromide) and an anionic (disulfine blue VN150) dye can be used in an acid and basic medium [105]. 

C18-0102. A solution has a pH of 8.5. What would be the color of the solution if the following indicators were present in the solution (a) methyl orange (b) phenol red (c) bromocresol green and (d) thymol blue (See Table 18-2. )... 

Add 2-3 drops of phenol red indicator. The solution should be red in color. Place a piece of white paper under the beaker to view the color of the solution better. 

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