(cher' ee joos).
» Cherry Juice is the liquid expressed from the fresh ripe fruit of Prunus cerasus L. (Fam. Rosaceae). It contains not less than 1.0 percent of malic acid (C4H6O5).
Coarsely crush washed, stemmed, unpitted, sour cherries in a grinder so as to break the pits but not mash the kernels. Dissolve 0.1 percent of Benzoic Acid in the mixture, and allow to stand at room temperature until a small portion of the filtered Juice, when mixed with one-half of its volume of alcohol, does not become cloudy within 30 minutes. Press the Juice from the mixture, and filter it.
Packaging and storage Preserve in tight, light-resistant containers, and prevent exposure to excessive heat.
Labeling The label states the Latin binomial name and, following the official name, the part of the plant source from which the article was derived.
Identification Add lead acetate TS to 5 mL of Juice until the mixture, when filtered, gives no further precipitation with the lead acetate solution. Filter, and to the clear filtrate add 5 mL of sodium oxalate solution (1 in 10) to remove the excess lead. Filter, add 5 mL of alkaline cupric tartrate TS to 5 mL of the clear filtrate, and warm: a red precipitate is formed.
Specific gravity 841: between 1.045 and 1.075.
Refractive index 831: not less than 1.350.
pH 791: between 3.0 and 4.0.
Residue on ignition 281: between 0.35% and 0.55%.
Arsenic, Method I 211: 0.3 µg per g, the Test Preparation being prepared as follows.
Test Preparation To 10 mL in a Kjeldahl flask add 5 mL of nitric acid and 5 mL of sulfuric acid, and heat the mixture until the volume is reduced to about 5 mL and the color becomes brownish or black. Add a small portion of nitric acid, and continue the heating, adding small portions of nitric acid as often as browning recurs, until the organic matter is destroyed, and dense, white fumes are liberated. Dilute the solution with about 10 mL of water, add 200 mg of ammonium oxalate, and continue the heating until dense, white fumes again are evolved and the solution is colorless to pale yellow. Cool, cautiously add water to make 20 mL, and mix.
Test Preparation Add 1.0 mL of Juice to 10 mL of nitric acid in a 250-mL conical flask, and boil for 5 to 10 minutes. Cool in an ice bath, and transfer to a separator with the aid of 5 mL of lead-free water.
Procedure Proceed as directed in the chapter, except to use 15 mL of Ammonium Citrate Solution, 500 µL of Hydroxylamine Hydrochloride Solution, and 3 mL of Potassium Cyanide Solution: not more than 5 µg per mL.
Limit of nonvolatile residue Evenly spread 5.0 mL over the bottom of a tared half Petri dish, and place on a steam bath for 1 hour. Dry in a vacuum desiccator over silica gel for 16 hours: the weight of the residue is not less than 500 mg. Not more than about 9.5% is found.
Limit of volatile acids Distill 25 mL of Juice with steam to obtain 100 mL of distillate, add phenolphthalein TS, and titrate with 0.10 N sodium hydroxide: not more than 1.5 mL is required.
Assay for malic acid Place 10.0 mL of Juice in a 125-mL flask, and add 1 g of calcium carbonate. Heat on a steam bath for 15 minutes, mixing occasionally, and pass through a filter. Wash the filter with five 5-mL portions of water, and to the combined filtrate and washings add 1 mL of 6 N ammonium hydroxide and 15 mL of ammonium oxalate TS. Heat on a steam bath for 15 minutes, pass through hardened filter paper, and wash the flask and the filter with five 5-mL portions of a solution prepared by mixing 1 mL of 6 N ammonium hydroxide with 49 mL of water. Puncture the filter paper, and wash the precipitate into the same flask by means of hot water, followed by 30 mL of 12 N sulfuric acid. Heat the solution to 80, and titrate with 0.1 N potassium permanganate VS. Each mL of 0.1 N potassium permanganate is equivalent to 6.704 mg of C4H6O5.