obtainable. Devine's method avoids this danger. For this method three standard solutions are used:

1. Tenth-normal hydrochloric acid.

2. Tenth-normal caustic soda or potash in alcohol.

3. Tenth-normal stearic acid in alcohol.

Solution No. 1 is used to standardize No. 2; Nos. 2 and 3 should be titrated against one another warm, using phenolphthalein as indicator.

inch The

Weigh 2 grams of soap (which needs no drying) into a round-bottomed flask of about 300 cc capacity, and pour 50 cc of alcohol upon it. Run in sufficient tenth-normal stearic acid from a burette to neutralize the free alkali in 2 grams of the soap, add some phenolphthalein, and stopper the flask with a cork stopper through which passes a glass tube about 30 inches long and of about internal diameter, having the lower end ground to a point on a grindstone. purpose of the tube is to serve as a reflux condenser. Place the flask and contents on a steam bath and heat for thirty minutes. At the expiration of this time the solution should be quite clear and show no alkali with the phenolphthalein. If the solution turns red during the boiling, showing that an insufficient quantity of stearic acid has been added at first, add more of that solution until the color disappears, then several cubic centimeters in excess, and heat twenty minutes longer. Remove the flask from the bath and, after cooling it a few minutes, titrate with tenth-normal caustic soda. The difference between the number of cubic centimeters of stearic acid solution added and the number of cubic centimeters of caustic soda used to neutralize it is equivalent to the total free alkali present.

While the first flask is heating, weigh in a similar flask 2 grams of soap, add 50 cc of alcohol, and place on the steam bath. When the first test is finished, calculate roughly the total alkali, assuming the total quantity to be carbonate. Now add to the second flask sufficient 10 per cent barium chlorid solution to precipitate the alkali found, heat a few minutes, add phenolphthalein, and titrate with tenth-normal stearic acid. The titration must take place slowly and with thorough agitation of the liquid because the sodium or potassium hydroxid reacts with the barium chlorid added and forms sodium chlorid and barium hydroxid. The latter is not very soluble in the alcoholic liquid, and sufficient time and pains must be taken to insure its complete neutralization by the stearic acid. Make a blank test on 50 cc of the alcohol, since this frequently contains carbon dioxid, and add the amount of tenthnormal caustic soda necessary to neutralize the free acid in this quantity of alcohol to the reading of the stearic acid burette in the second test. This corrected reading gives the number of cubic centimeters of tenth-normal stearic acid used to neutralize the caustic alkali in 2 grams of soap. The difference between the total alkali found and the caustic soda will, of course, give the carbonate. For example: To 2 grams of soap and 15 ce of tenthnormal stearic acid add 3.2 ce of tenth-normal caustic soda to neutralize. Then 15 cc-3.2 cc 11.8 cc of tenth-normal stearic acid equivalent to total free alkali.

To neutralize the caustic soda in the sample treated with barium chlorid 4.1 cc of tenth-normal stearic acid was required. Fifty cubic centimeters of the alcohol used required 0.2 cc of tenth-normal caustic soda, hence the total is 4.3 cc. Since it requires 4.3 cc of tenth-normal stearic acid to neutralize free caustic alkali, 11.8 cc-4.3 cc = 7.5 cc of tenth-normal stearic acid required to neutralize the carbonated alkali.

a J. Amer. Chem. Soc., 1900, 22:693.

1 One cubic centimeter of tenth-normal stearic acid corresponds to 0.0122 gram BaCl2 211:0 or 0.122 ce of a 10 per cent barium chlorid solution,

=

One cubic centimeter of tenth-normal stearic acid 0.004 gram of caustic soda or 0.0053 gram of sodium carbonate. These figures calculated to percentage would be: 0.86 per cent of caustic soda and 1.99 per cent of sodium carbonate.

It is to be noted that a rubber stopper can not be used in the flasks used for dissolving the soap on account of the sulphur in the rubber which decolorizes an alcoholic solution of phenolphthalein. The method is applicable to all soaps that do not contain fillers which react with the standard solutions employed.

7. Unsaponified Matter.

Dissolve 5 grams of soap in 50 cc of 50 per cent alcohol; if any free fatty acids are present add just enough standard alkali to neutralize them and wash into a separatory funnel with 50 per cent alcohol. Extract with 100 cc of gasoline (B. P. 50°-60°). Wash the gasoline with water, evaporate, and weigh as unsaponified. This may consists of fat that has not been converted into soap or

of hydrocarbon oils.

8. Rosin.

If much unsaponified matter is present, prepare dry fatty and rosin acids from the portion from which the unsaponified matter has been removed. Dissolve 3 grams of the dry mixed acids in 25 cc of absolute alcohol in a 100 cc stoppered flask, place the flask in cold water and shake; add 25 ce of absolute alcohol saturated with dry hydrochloric acid, shake occasionally, and let the action go on for twenty minutes; then add 10 grams of dry granular zinc chlorid, shake, and allow to stand for twenty minutes. Pour the contents of the flask into 200 cc of water in a 500 cc beaker, and rinse out the flask with dilute alcohol. Put a small stick of metallic zinc in the beaker and boil off the alcohol. Cool, transfer to a separatory funnel, extract with gasoline, wash the gasoline until free from hydrochloric acid, distil off the gasoline, dissolve in neutral alcohol, and titrate with standard alkali using phenolphthalein as indicator. (One cubic centimeter of normal alkali corresponds to 0.346 gram of rosin.) The rosin may be determined gravimetrically by washing the gasoline extract with water. It is not necessary to wash absolutely free from acid. Then treat the extract in the funnel with a solution of 5 grams of potassium hydroxid and 5 cc of alcohol in 50 cc of water. Upon shaking, the rosin is rapidly saponified and the two layers separate well. Draw off the rosin soap, wash the gasoline once with water, add the washings to the soap solution, add an excess of acid, extract the rosin with gasoline, evaporate the gasoline, and weigh the rosin.

9. Silica and Silicates.

Insoluble silicates, sand, etc., are present in the insoluble; but sodium silicate fillers will only show by forming pasty liquids. When sodium silicate is suspected, ash the soap (10 grams), add an excess of hydrochloric acid to the ash, evaporate to dryness; add hydrochloric acid and again evaporate to dryness; cool, moisten with hydrochloric acid, dissolve in water, filter, wash, evaporate the filtrate to dryness, and again take up with hydrochloric acid and water, filter, and wash. Unite the precipitates, ignite, and weigh as silicon dioxid; calculate to sodium silicate (Na:Si,O). If metals other than the alkalis are suspected, the filtrate from the silica determination may be examined.

10. Glycerin.

Dissolve 20 to 25 grams of soap in hot water, add a slight excess of sulphuric acid, and heat on a water bath until the fatty acids separate in a clear layer. Remove the fatty acids and filter the acid solution into a graduated flask. Remove the chlorids and the soluble fatty acids by adding crystals of silver sulphate, cool, make up to the mark, mix, allow to settle, filter through dry paper, take an aliquot corresponding to 5 grams of soap, and determine by Hehner's bichromate method (see under Glycerin). This method can not be used when sugar is present as it also would reduce the bichromate. When sugar is present, remove the fatty acids as just described, neutralize an aliquot with milk of lime, evaporate to about 10 cc, add 2 grams of sand and milk of lime containing about 2 grams of calcium hydroxid, and evaporate almost to dryness. Treat the moist residue with 5 cc of 96 per cent alcohol, rub the whole mass into a paste, heat the mixture on a water bath stirring constantly, and decant the liquid into a 250 cc flask, wash the residue five or six times with small portions of alcohol, cool the contents of the flask to 15°, fill to the mark with 96 per cent alcohol, mix, and filter through a dry paper; evaporate 200 cc of the filtrate to a sirupy consistency on a water bath, transfer to a stoppered cylinder with 20 cc of absolute alcohol, add three portions of 10 cc each of absolute ether, mixing after each addition; let stand until clear, pour off through a filter, and wash the cylinder on the filter with a mixture of two parts of absolute alcohol and three parts of absolute ether. Evaporate to a sirup, dry for one hour at the temperature of boiling water, weigh, ignite, and weigh again. The loss multiplied by 5/4 is the weight of the glycerin in the aliquot taken. Instead of weighing the glycerin it can be titrated after driving off the alcohol and ether.

11. Sugar.

Dissolve 5 grams of soap in water, add an excess of hydrochloric acid, heat on a steam bath for thirty minutes, cool, separate the fatty acids, and make up to a definite volume. Add an aliquot, depending upon the amount of sugar supposed to be present, to 50 cc of a mixed Soxhlet solution, make the total volume 100 cc, heat to boiling, boil two minutes, filter on a weighed gooch, wash with water, then with alcohol and ether, dry at 100° for thirty minutes, cool, and weigh the cuprous oxid. Calculate the percentage of sugar as invert sugar according to Munson and Walker's tables."

a J. Amer. Chem. Soc., 1906, 28: 663-686.

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