Phenol phthalein acidity

C) Phenacyl and p-Bromophenacyl esters. Ammonium salts in aqueous-ethanolic solution do not however usually condense satisfactorily with phenacyl and />-bromophenacyl bromide. The aqueous solution of the ammonium salt should therefore be boiled with a slight excess of sodium hydroxide to remove ammonia, and the solution then cooled, treated with hydrochloric acid until just alkaline to phenol-phthalein, and then evaporated to dryness. The sodium salt is then treated as described (p. 349) to give the ester. Filter the ester, and wash with water to remove senium halide before recrystallisation. 

Benzylthiouronium salts. Add 0 5 g. of sulphanilic acid to 10 ml. of water and 5 ml. of 10% NaOH solution, zndgently warm the shaken mixture until a clear solution is obtained. Cool, add 1 drop of phenol-phthalein solution, and then add dilute HCl dropwise with shaking until the pink colour is just discharged. Now add very dilute NaOH solution until the pink colour yt/rZ returns. Cool and add with shaking a solution of 0-5 g. of benzylthiouronium chloride in 5 ml. of water. The thiouronium salt rapidly separates filter at the pump, wash with water, drain and recrystallise from ethanol. Colourless crystals, m.p. 185°. (M.ps., p. 548.)... 

The method is based on the conversion of urea to amnionium carbonate and the estimation of the latter by titration with standard acid. For this purpose, two equal quantities of urea (or urine) are measured out into two flasks A and B. A is treated with 10 ml. of a strong urease preparation and some phenol-phthalein, warm water is added and the mixture is adjusted by the addition of V/io HCl from a burette A until the red colour is just discharged. This brings the mixture to about pH 8 (the optimum for urease) and also prevents loss of ammonia. 

The above simple experiments illustrate the more important properties of aliphatic acid chlorides. For characterisation, the general procedure is to hydrolyse the acid chloride by warming with dilute alkali solution, neutralise the resulting solution with dilute hydrochloric acid (phenol-phthalein), and evaporate to dryness on a water bath. The mixture of the sodium salt of the acid and sodium chloride thus obtained may be employed for the preparation of solid esters as detailed under Aliphatic Acids, Section 111,85. The anilide or p-toluidide may be prepared directly from the acid chloride (see (iii) above and Section III,85,i). 

To the same solution add a few drops of phenol phthalein, and titrate it against N/10 NaOH until a pink colour appears, which will indicate the total acidity of the bath. This is approximately 35 to 37 for a concentration of 5% for a hot process and 60 to 64 for a concentration of 10% for a cold process. Obtain the standard total acidity of the hot or cold process chemicals from the manufacturer. 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

Dissolve a sample containing 0.5 meq anion-active material with a ether carboxylic acid group in alcohol and neutralize with 0.5 N NaOH on phenol-phthalein. Transfer this solution to a 250-ml graduated flask with a stopper and make up to the mark with distilled water. Introduce into a 100-ml graduated cylinder with a stopper ... 

Irreversible reaction of [18] iodine with acetylsalicylic acid, aethaverine, amidopyrine, ascorbic acid, benzo-caine, quinine, dihydrocodeine, fluorescein, glycine, hydrocortisone acetate, isoni-azid, metamizole, papaverine, paracetamol, phenacetin, phenol-phthalein, piperazine, resorcinol, salicylic acid, salicylamide, sulfaguanidine, thymol, triethanolamine, tris buffer detection by reaction chromatography... 

A. Lithium triethylcarboxide (Solution 1). A thoroughly dried, 1-1., three-necked, round-bottomed flask is fitted with a septum inlet with serum cap, a reflux condenser, and a magnetic stirrer. The flask is purged with and maintained under an atmosphere of dry nitrogen. A solution of 300 ml. of 1.66 M butyllithium (0.50 mole) in hexane (Note 1) is introduced into the flask by syringe (Note 2) and cooled to 0° in an ice bath. Then 58 g. (0.50 mole) of 3-ethyl-3-pentanol (Note 3) is added slowly but constantly by syringe (Note 4). At the end of addition the yellow tint of the butyllithium solution disappears. The alkoxide solution is standardized by hydrolysis of aliquots in water and by titration of the resulting lithium hydroxide with standard acid to a phenol-phthalein end point (Note 5). 

CHjC0.NH C6H N02 +CH,COOH After allowing to stand for 1 hr, add distd w through the condenser in an amt sufficient to hydrolyze surplus anhydride to acetic acid. Transfer to a 1 1 vol flask and dilute to the mark. Pipette an aliquot into a beaker and titrate with N/10 NaOH soln in presence of an indicator, such as phenol-phthalein. Take the burette reading (Rj). Run a blanc by titrating with N/10 NaOH the same quantity of acetic anhydride... 

When NaOH(a ) is added to CH3C02H(aacid-base indicator phenol-phthalein, the color of the indicator changes from colorless to pink in the pH range 8.2-9.8 because of neutralization of the acetic acid. 

Acidity.—From 5 to 10 grams of the oil are dissolved in neutral alcohol and the acidity measured with N/10-alkali in presence of phenol-phthalein. 

Considerable heat is evolved in the neutralization of the acid with the sodium hydroxide. The extraction can be carried on faster and without loss if the solution is cooled by the direct addition of ice. It is convenient to test the extracts with phenol-phthalein to determine when all of the acid has been removed. 

See Carboxylic acids, Section 9.6.15, p. 1264.) If the substance is the free sul-phonic acid, dissolve 0.5 g of it in 5-10 ml of water, add a drop or two of phenol-phthalein indicator and neutralise with c. m sodium hydroxide solution. Then add 2-3 drops of 0.1 m hydrochloric acid to ensure that the solution is almost neutral (pale pink colour) under alkaline conditions the reagent tends to decompose to produce the evil-smelling phenylmethanethiol. 

Estimation of Atmospheric Carbon Dioxide.—A convenient method is that of Pettenkofer,4 which consists in introducing a standard solution of barium hydroxide into a large bottle containing several litres of the air to be examined. The bottle is shaken from time to time to keep the sides moistened wit-h the solution, and after 5 or 6 hours the absorption of carbon dioxide may be regarded as complete. The baryta solution is decanted into a small stoppered bottle and allowed to stand until any suspended barium carbonate has settled. A portion of the clear liquid is then removed and titrated with dilute sulphuric acid, using phenol-phthalein as indicator. The diminution in alkalinity due to combination with carbonic acid is thus measured, and from the data obtained the percentage of carbon dioxide m the atmosphere may easily be calculated. 

Acidity (as acetic acid) Mix 38 mL of sample with an equal volume of carbon dioxide-free water, add 0.1 mL of phenol-phthalein TS, and titrate with 0.1 A sodium hydroxide. Not more than 0.1 mL is required to produce a pink color. Aldehydes (as formaldehyde) Prepare a Sample Solution by diluting 2.5 mL of sample with 7.5 mL of water. Prepare a Standard Solution containing 40 p,g of formaldehyde in 10 mL of water. Add 0.15 mL of a 5% solution of 5,5-dimethyl-1,3-cyclohexanedione in alcohol to each solution, and evaporate on a steam bath until the Acetone is volatilized. Dilute to 10 mL with water, and cool quickly in an ice bath while stirring vigorously. Any turbidity produced in the Sample Solution does not exceed that produced in the Standard Solution. 

Assay With the aid of 10 mL of water, quantitatively transfer about 500 mg of sample, accurately weighed, into a separator Add 2 mL of 2.7 A hydrochloric acid, and extract the precipitated saccharin, first with 30 mL, then with five 20-mL portions of a solvent comprising 9 1 (v/v) chloroform alcohol. Filter each extract through a small filter paper moistened with the solvent mixture, and evaporate the combined filtrates to dryness on a steam bath with the aid of a current of air. Dissolve the residue in 75 mL of hot water, cool, add phenol-phthalein TS, and titrate with 0.1 A sodium hydroxide. Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1A sodium hydroxide is equivalent to 20.02 mg of C7H8N203S. Benzoate and Salicylate Add 3 drops of ferric chloride TS to 10 mL of a 1 20 aqueous solution previously acidified with 5 drops of glacial acetic acid. No precipitate or violet color appears. 

Acid Value If the sample is plastic or semisolid, soften a portion by warming it in a water bath at a temperature not exceeding 60°, and then mix it thoroughly. Transfer about 2 g of a well-mixed sample, accurately weighed, into a 250-mL Erlenmeyer flask, and dissolve it in 50 mL of petroleum ether. Add 50 mL of ethanol, previously neutralized to phenol-phthalein with 0.1 N sodium hydroxide, to this solution, and mix well. Using phenolphthalein TS as the indicator, titrate with 0.1 N sodium hydroxide to a pink endpoint that persists for 5 s. Calculate the Acid Value by the formula... 

Acidity Dissolve 1.0 g of sample in 25 mL of a 1 1 (v/v) alcohokether mixture that has been neutralized to phenol-phthalein TS with 0.1 N sodium hydroxide. Add 0.5 mL of phenolphthalein TS, and titrate with 0.1 A sodium hydroxide until the solution remains faintly pink after shaking for 30 s. Not more than 1.0 mL of 0.1 A sodium hydroxide is required. Lead Determine as directed in the Flame Atomic Absorption Spectrophotometric Method under Lead Limit Test, Appendix MB, using a 10-g sample. 

Procedure Unless otherwise directed in the individual monograph, transfer about 4 g of the sample, previously crushed into small lumps and accurately weighed, into a 250-mL Erlenmeyer flask, and add 100 mL of a 1 3 mixture of toluene-isopropyl alcohol, previously neutralized to phenol-phthalein TS with sodium hydroxide. Dissolve the sample by shaking or heating gently, if necessary, then add about 0.5 mL of phenolphthalein TS, and titrate with 0.5 N or 0.1 N alcoholic potassium hydroxide to the first pink color that persists for 30 s. Calculate the acid number by the formula... 

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