Phenolphthalein solution

Sorensen s reaction. First read carefully the Estimation of Glycine, p. 463. Dissolve 0 2 g. of glycine in a few ml. of water in a test-tube A, add 2 drops of phenolphthalein and then very dilute NaOH solution drop by drop until the solution just turns pink. In a second test-tube B place 2 ml. of 40% formalin solution, add 2 drops of phenolphthalein solution and then the dil. NaOH solution until the solution just turns pink. Pour the contents of B into A and note the immediate decolorisation of the phenolphthalein, the solution now being acid. Observe also that several drops of dil. NaOH solution can now be added before the pink colour is restored. 

Weigh out accurately about 2-5 g. of pure powdered succinic acid, transfer to a 100 ml. graduated flask, dissolve in distilled water, make the solution up to the graduation mark and mix well. Now, by means of a pipette, transfer 25 ml. of the solution to a 150 ml. conical flask, add a drop of phenolphthalein solution and titrate with A/ 2 NaOH or KOH solution to obtain consistent results. 

Place about 50 ml. of 40% formalin solution in a conical flask and add at least 10 drops of phenolphthalein solution. No add ery carefully from a burette dilute sodium hydroxide solution (il/ 10 will serve the purpose) until the solution is just faintly pink. 

The estimation. Label two 250 ml. conical flasks A and B, and into each measure 5 ml. of urine solution (or about o i g. of solid urea, accurately weighed). Add to each about 20 ml. of water and bring the temperature to about 60°. To A add 3 drops of phenolphthalein solution and to B add i ml. of 0-5% mercuric chloride solution. Now to each solution, add 10 ml. of the urease solution and mix well. The mixture A soon turns red. 

The distillate is collected in a 500 c.c. Erlenmeyer flask having a mark upon it to indicate the level of 250 c.c. Phenolphthalein solution and a sufficient excess of deci-normal sodium hydroxide solution are added to the distillate and the excess of alkali determined by titration. 

Mixed indicator solution. Mix two volumes of 0.1 per cent phenolphthalein solution and three volumes of 0.1 per cent thymol blue solution (both in ethanol). 

Procedure. Weigh out accurately about 4 g of the pure organic acid, dissolve it in the minimum volume of water (Note 1), or 1 1 (v/v)ethanol/water mixture, and transfer the solution to a 250 mL graduated flask. Ensure the solution is homogeneous and make up to the required volume. Use a pipette to measure out accurately a 25 mL aliquot and transfer to a 250 mL conical flask. Using two drops of phenolphthalein solution as indicator, titrate with standard 0.2M (approx.) sodium hydroxide solution (Note 2) until the colourless solution becomes faintly pink. Repeat with further 25 mL volumes of the acid solution until two results in agreement are obtained. 

Add 2 drops of phenolphthalein solution to each solution in each of the numbered test tubes. 

Add 3 drops of phenolphthalein solution to the flask containing the acid solution. Place the flask under the burette so that the tip of the burette is 1-2 cm inside the mouth of the flask. 

Phenolphthalein solution is toxic and flammable. Be sure no open flames are in the lab when phenolphthalein solution is in use. 

Litmus was probably the most popular choice of acid-base indicator, but it is not a good choice for colour-blind chemists. The use of phenolphthalein as an acid-base indicator comes a close second. Phenolphthalein (XIII) is another weak organic acid. It is not particularly water soluble, so we generally dissolve it in aqueous ethanol. The ethanol explains the pleasant, sweet smell of phenolphthalein solutions. 

Fluoroacetic acid.1 A few drops of phenolphthalein solution are added to a mixture of methyl fluoroacetate (46-0 g., 0-5 mol.) and water (100 c.c.) and then powdered barium hydroxide octahydrate (78-9 g., 0-25 mol.) is added in small portions, the mixture being mechanically stirred after each addition until the alkaline reaction has disappeared. The resultant liquid is then made acid, if necessary by the addition of a few drops of methyl fluoroacetate, filtered and the filtrate concentrated to about 100 c.c. on a water-bath. The liquid is cooled and methylated spirit (500 c.c.) added in order to precipitate the barium fluoroacetate, which is filtered off, drained and dried, but not recrystallized yield 69-0 g. (95-0 per cent). 

In the meantime, a sodium sulfite solution is prepared by dissolving 890 g. of sodium hydroxide, of about 90 per cent purity, in about 1 1. of water and then diluting to 6 1. A few drops of phenolphthalein solution are added and sulfur dioxide passed in, first until an acid reaction is indicated and then for two or three minutes longer. During the addition of the sulfur dioxide, the solution is cooled with running water. On account of the strong alkaline solution, the original color produced by... 

A sample of a solid, weak monoprotic acid, HA, is supplied, along with solid sodium hydroxide, a phenolphthalein solution, and primary standard potassium hydrogen phtha-late (KHP). 

Procedure Weigh accurately about 1.5 g of sodium hydroxide and dissolve in about 40 ml of carbon-dioxide free distilled water (i.e., boiled and cooled DW). Cool and titrate with 1 N sulphuric acid using phenolphthalein solution as indicator. When the pink colour of the solution is discharged record the volume of acid solution required. 

N sodium hydroxide using phenolphthalein solution as indicator. Each millilitre of 0.1 N sodium hydrox-... 

Materials Required Chloral hydrate 4.0 g sodium hydroxide (N) 30 ml sulphuric acid (N) phenolphthalein solution (1.0% w/v in 50% v/v alcohol) 0.1 N silver nitrate solution potassium chromate solution (5% w/v in water). 

Procedure Weigh accurately about 4 g of chloral hydrate and dissolve in 10 ml of DW and add 30 ml of N sodium hydroxide solution. Allow the resulting mixture to stand for 2 minutes, and then titrate with N sulphuric acid, employing phenolphthalein solution as indicator till a colour change from pink to colourless is achieved. Titrate the neutralized liquid thus obtained with 0.1 N silver nitrate using potassium chromate solution as indicator till precipitation of red chromate is obtained, Add, now 2/15th of the amount of 0.1 N silver nitrate used to the amount of N sulphuric acid used in the first titration and deduct the figure so obtained... 

Materials 150-mL beaker, stirring rod, liquid dishwashing detergent, calcium carbide, forceps, wood splints, matches, ruler about 40 cm long, rubber band, phenolphthalein solution... 

Rinse the beaker thoroughly, then add 25 mL distilled water and a drop of phenolphthalein solution. Use forceps to place a small piece of CaC2 in the solution. Observe the results. 

To transfer a small amount of indicator to the acid solution, place one drop of phenolphthalein solution on a watch glass. Touch the drop with the glass rod. Transfer this small amount of indicator to the HCl in the beaker. 

A solution of 3 ml (14 mmol) of freshly distilled sebacoyl dichloride (for preparation see above) in 100 ml of carbon tetrachloride is placed in a 250 ml beaker. A solution of 4.4 g (38 mmol) of hexamethylenediamine in 50 ml of water is carefully run on to the top of this solution, using a pipette. (The aqueous solution can be made more readily visible by coloring it with a few drops of phenolphthalein solution.) A polyamide film is immediately formed at the interface and can be pulled out from the center with tweezers or clamps and laid over some glass rods it can now be pulled out continuously in the form of a hollow thread and wound up on to a spool driven by a slow-running motor. The polycondensation comes rapidly to a standstill if the motor is stopped, but immediately recommences, even after some hours, when the motor is restarted. 

When following the procedure established by the Indian Pharmacopoeia 1996 [13], about 0.1 g of analyte is accurately weighed and dissolved in 15 mL of warm 95% ethanol (previously neutralized to phenolphthalein solution). One adds 20 mL of water and titrates with 0.5 M NaOH using phenolphthalein solution as the indicator. Each milliliter of 0.5 M NaOH titrant is equivalent to 0.06106 g of benzoic acid. 

The British P 1993 [15] describes a procedure to determine benzoic acid in benzoic acid ointment that also contains salicylic acid. In this method, 2 g of the ointment is added to 150 mL water, and warmed until melted. The solution is titrated with 0.1 M NaOH, using phenolphthalein solution as the indicator. Salicylic acid is assayed by a spectrophotometric procedure, and its content subtracted from the total acid value to obtain the benzoic acid content. 

Pour 2-3 ml each of 1 iV solutions of hydrochloric and acetic acids, sodium hydroxide, and an aqueous ammonia solution into test tubes. Pour one or two drops of a phenolphthalein solution into each of the tubes and see whether the colour of the solution changes. Perform similar experiments with other indicators, namely, methyl red, litmus, methyl orange (see Appendix 1, Table 6). Enter your observations into your laboratory notebook using Form 14. 

The completion of the oxidation should be tested by adding 1 drop of an alcoholic phenolphthalein solution and 3 drops of water to 1 drop of the oxidation mixture on a porcelain spot plate. Amine oxides give no color with phenolphthalein. 

Procedure All solutions should be fresh. Prepare a solution of formaldehyde by diluting 9 mL of 37 wt% formaldehyde to 100 mL. Dissolve 1.5 g of NaHSO,10 and 0.18 g of Na,SO, in 400 mL of water, and add 1 mL of phenolphthalein solution (Table 11-4). Add 23 mL of formaldehyde solution to the well-stirred buffer solution to initiate the clock reaction. The time of reaction can be adjusted by changing the temperature, concentrations, or volume. 

Prepare a fresh solution from 1.6 g of KI, 20 mL of water, 5 mL of 1 wt% starch solution, and 5 mL of phenolphthalein indicator solution. (If the solution darkens after several days, decolorize it with a few drops of dilute Na2S203.) Soak the three layers of paper with the Kl-starch-phenolphthalein solution. Connect the stylus and foil to a 12-V DC power source, and write on the paper with the stylus. 

Sensitiveness. — To 250 cc. of water, which has been well-boiled and then cooled, add 3 to 5 drops of phenolphthalein solution the solution should not require more than 0.05 cc. of decinormal potassium hydroxide to effect a change from colorless to violet (not red). 

On adding to a solution of 0.5 gm. of potassium iodide in 10 cc. of water 1 drop of phenolphthalein solution, no red color should develop. 

The solution of 1 gm. of sodium acetate in 1 cc. of water is alkaline to litmus paper it should, however, not be reddened, or only very slightly, by phenolphthalein solution. 

---