Phenolphthalein paper

Simple indicator papers only show if a solution is acidic, neutral, or alkaline. Examples of this type are litmus paper, phenolphthalein paper, and congo paper. 

Leaks can be detected at once by ammonia odor unless there is already an appreciable amount of ammonia in the ak. Leaks can be exactiy located by using either moist phenolphthalein paper or an open bottie of hydrochloric acid. If a serious ammonia leak is discovered, a large column of water apphed through a fire hose having a spray nozzle can be used to absorb the vaporized ammonia. 

Another recipe for a universal indicator is as follows 0.05 g of methyl orange, 0.15 g of methyl red, 0.3 g of bromothymol blue, and 0.35 g of phenolphthalein in 1 L of 66 per cent ethanol. The colour changes are pH up to 3, red pH 4, orange-red pH 5, orange pH 6, yellow pH 7, yellowish-green pH 8, greenish-blue pH 9, blue pH 10, violet pH 11, reddish-violet. Several universal indicators are available commercially as solutions and as test papers. 

Indicators are chemical dyes that change color with a change of pH. Litmus paper and phenolphthalein are two common indicators used in acid-base reactions. They are chosen because they change color at or very near solution neutrality. Litmus paper is red in acidic solutions and blue in basic solutions. Phenolphthalein is colorless in acidic solutions and turns red in basic solutions. 

Although litmus paper, cabbage juice, and phenolphthalein can indicate whether a substance is acidic or basic, they have limitations in that they cannot determine an exact pH. To do this, an acid-base indicator called universal indicator can be used. Universal indicator is actually a mixture of several different acid-base indicators (usually phenolphthalein, methyl red, bromthymol blue, and thymol blue). This mixture produces a wide range of colors to indicate different pHs. Under very acidic conditions, universal indicator is red. It turns orange and then yellow between the pHs of 3 to 6. It is green at neutral pH and turns greenish-blue as a solution becomes more alkaline. In very basic conditions, universal indicator turns a dark purple color. 

To purify the soap 20-30 g. are dissolved in boiling water, salted out from the hot solution, and again allowed to solidify. In this way the small amount of alkali in the crude product is removed. The soap, however, remains alkaline to litmus and turmeric papers. The hydrolysis of the quite pure soap is, however, not sufficiently extensive, the concentration of OH-ions not sufficiently large, for phenolphthalein to be coloured. 

Experiment.—Dissolve 1 c.c. of nitromethane in water and test the solution with litmus paper. Then add some phenolphthalein and, drop by drop from a burette, OliV-sodium hydroxide solution. Before a permanent pink colour develops about 2 c.c. of the alkali will be added—a sign that an acid, aci-nitromethane, H2C NOOH, has been formed from the neutral nitromethane. A small sample of this solution gives with ferric chloride a blood-red colour, characteristic of aci-nitro-compounds. The salts of the oci-compound undergo extensive hydrolysis. This is shown by further addition of 0-1 N-alkali which produces a deep red colour. If 10 c.c. of alkali were added and 5 c.c. of 0-1 JV-hydrochloric acid are now run in the solution is decolorised because the liberated oci-compound restricts the hydrolysis of its salt. But the conversion of H2C N02H into H3C.N02 proceeds so rapidly that the red colour reappears in a few moments. 

Desoxycholic Acid, Fatty Acids, Cholesterol.—The first alcoholic filtrate obtained during the crystallisation of the cholic acid (see above) is made strongly alkaline to phenolphthalein paper with 2 N-sodium hydroxide solution and concentrated to a syrupy consistency in a porcelain basin on the water bath. The syrup is taken up in 250 c.c. of water, transferred to a separating funnel, cooled, covered... 

Pour about 10 mL of NH3(aq) into a small beaker. Place the beaker on a sheet of white paper. Add 2 drops of phenolphthalein indicator. 

The pH of a solution may be estimated from color indicators that change hue with pH, like litmus or phenolphthalein papers see Table 10-2. Where precise values are required, an electrical pH meter is utilized. 

The usual method of testing neutrality by means of litmus or phenolphthalein paper is not applicable when the pH of the material is around 7.0- Litmus paper does not turn red until die acidity is between approx pH 4 and 6, and phenolphthalein paper does not change color until the acidity is between approx pH 8 and 10... 

Upon completion of the reaction, filter the solution through a paper filter and add a few drops of phenolphthalein to it. What is observed ... 

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. 

A clear, colorless, liquid, of specific gravity 1.235 to 1.240. Lead subacetate solution is alkaline to litmus paper, but does not redden phenolphthalein. 

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. 

POUR 10 ml OF THE SOAP AND DETERGENT SOLUTIONS INTO SEPARATE TEST TUBES. TEST EACH SOLUTION FOR ACID AND BASE WITH LITMUS PAPER AND PHENOLPHTHALEIN. 

The alkalinity of the deeply colored solution can be tested with phenolphthalein paper. The edges of the wetted paper become visibly red. One should be sure to test the aqueous solution and not the separated thiazole floating on top of the liquid. 

Isolation of Calcium Salt.—The milk of lime is now carefully added with stirring until the solution is just neutral (test with phenolphthalein paper). It is then boiled, and after cooling to 60° the CaS04 is filtered off on a Buchner funnel, and washed with a little hot water. 

Phenolphthalein Paper.—Used in acidimetry and alkalimetry. Turned red by alkalis, reacting with ammonia and sodium carbonate, but not with bicarbonate. Used chiefly in analytical work. 

Evaluation.—5 gms. sodium sulphide are dissolved in water up to 250 c.cs. and carefully neutralised with dilute acetic acid in presence of phenolphthalein until the latter is colourless. A N solution of crystallised zinc sulphate (57-514 gms. ZnSO TB O per litre) is run in from a burette until all the soluble sodium sulphide is converted into zinc sulphide. A cone, solution of cadmium sulphate is spotted on thick blotting-paper, and a drop of the liquid being analysed is placed near it. A yellow stain will be produced as long as any soluble sulphide remains. The zinc sulphate is added until no yellow colour is given. 

Acidity.—100 grams of the dextrin are treated with about 800 c.c. of boiling water and the solution titrated in the cold with normal caustic alkali either in presence of phenolphthalein or, with a coloured solution, with the help of litmus paper. The acidity is expressed in c.c. of normal alkali per 100 grams of substance. 

Alkalinity and Lime.—These are determined as in defecated juice, but for the alkalinity only 20-25 c.c. of juice are taken, and this is then diluted sufficiently to give a slightly coloured liquid. If the juice is so highly coloured that the change of colour with phenolphthalein cannot be detected with certainty, sensitive litmus paper is used and a drop of the liquid removed and tested from time to time during the titration. 

Acidity.—This is expressed in c.c. of normal soda solution per 100 grams of substance and is determined by titrating a solution of 10 grams in water with N/io-soda, using sensitive litmus paper or phenolphthalein as indicator. 

Total Acidity.—50 or 100 c.c. of the beer, freed from the bulk of the carbon dioxide, are heated for half an hour at 400 to expel the residual gas and are then titrated with N/io-sodium hydroxide, neutral litmus paper or phenolphthalein being used as indicator when phenolphthalein is employed, it is well to add a slight excess of the alkali and then to run in N/10-sulphuric add until the red coloration disappears. When, however, the liquid is too highly coloured to allow accurate observation of the point of neutrality, the procedure is as follows to 20 c.c. of distilled water, previously boiled, are added 10-12 drops of alcoholic phenolphthalein solution and 0 2 c.c. of N/io-sodium hydroxide. The beer is then titrated with the decinormal alkali and, after each addition of the latter, six drops of the liquid are added to one drop of the indicator prepared as above, placed in the depression of a porcelain plate the titration is finished when this indicator is no longer decolorised in this way. The acidity is usually 1 Race Joum. Soc. Chem. Industry, 190S, XXVII, p, 544. 

The flask A is immersed in a boiling water-bath and connected with a receiver, which is then evacuated by means of a water-pump Exactly 5 c c of the vinegar are next introduced into the funnel, allowed to flow into the flask, and there distilled until the volume is reduced to 2-3 c c, without interruption of the operation, 20 c c of distilled water are then introduced and the volume again reduced to 2-3 c c, two similar additions of distilled water being subsequently made When the volume in the flask is finally reduced to about 5 c c, the operation is stopped and the liquid transferred quantitatively into a conical flask, the fixed acidity being then determined by titration with N/io-sodium hydroxide either m presence of phenolphthalein or, with a highly coloured residue, with the help of litmus paper. 

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