10. Alkalinity of the Soluble Ash—Official
Cool the filtrate from 9 and titrate with N/10 hydrochloric acid, using methyl orange as an indicator.
Express the alkalinity in terms of the number of cc. of N/10 acid per 1 gram of the sample.
11. Soluble Phosphoric Acid in the Ash—Official
Acidify the solution of soluble ash, obtained in 9, with dilute nitric acid and determine phosphoric acid (P2O5). For percentages up to 5 use an aliquot corresponding to 0.4 gram of substance, for percentages between 5 and 20 use an aliquot corresponding to 0.2 gram of substance, and for percentages above 20 use an aliquot corresponding to 0.1 gram of substance. Dilute to 75–100 cc., heat in a water-bath to 60°–65° C., and for percentages below 5 add 20–25 cc. of freshly filtered molybdate solution. For percentages between 5 and 20 add 30–35 cc. of molybdate solution. For percentages greater than 20 add sufficient molybdate solution to insure complete precipitation. Stir, let stand in the bath for about 15 minutes, filter at once, wash once or twice with water by decantation, using 25–30 cc. each time, agitate the precipitate thoroughly and allow to settle; transfer to the filter and wash with cold water until the filtrate from two fillings of the filter yields a pink color upon the addition of phenolphthalein and one drop of the standard alkali. Transfer the precipitate and filter to the beaker, or precipitating vessel, dissolve the precipitate in a small excess of the standard alkali, add a few drops of phenolphthalein solution, and titrate with the standard acid.
12. Insoluble Phosphoric Acid in the Ash—Official
Determine phosphoric acid (P2O5) in the Insoluble ash by the foregoing method.
13. Chlorides—Official
Moisten 5 grams of the substance in a platinum dish with 20 cc. of a 5-percent solution of sodium carbonate, evaporate to dryness and ignite as thoroughly as possible at a temperature not exceeding dull redness. Extract with hot water, filter and wash. Return the residue to the platinum dish and ignite to an ash; dissolve in nitric acid, and add this solution to the water extract. Add a known volume of N/10 silver nitrate in slight excess to the combined solutions. Stir well, filter and wash the silver chloride precipitate thoroughly. To the filtrate and washings add 5 cc. of a saturated solution of ferric alum and a few cc. of nitric acid. Titrate the excess silver with N/10 ammonium or potassium thiocyanate until a permanent light brown color appears. Calculate the amount of chlorin.
14. Caffein—The Fendler and Stüber Method—Tentative