XX] FLAVORING EXTRACTS 263 



which come over. Store in a dark, cool place in well filled bottles. Twenty-five cc. 

 of this alcohol, on standing 20 minutes at 14°-16°C. with 20 cc. of the sulphite fuchsin 

 solution, should develop only a faint pink coloration. If a stronger color is de- 

 veloped, repeat the treatment with meta-phenylndiamin hydrochlorid as above. 



(b) Sulphite-fuchsin solution. — Dissolve 0.5 gram of fuchsin in 250 cc. of water, 

 add an aqueous solution of sulphur dioxid containing 16 grams of the gas, allow to 

 stand until colorless, or nearly so, and make up to 1 liter with water. Let stand 12 

 hours before using and keep in a refrigerator. This solution is liable to deteriorate 

 and should be reasonably fresh when used. 



(C) Standard citral solution. — Use 0.5 or 1 mg. of C.P. citral per cc. in 50% alde- 

 hyde-free alcohol. 



23 DETERMINATION. 



Weigh approximately 25 grams of the extract in a stoppered weighing flask, 

 transfer to a 50 cc. flask and make up to the mark at room temperature with alde- 

 hyde-free alcohol. Measure, at room temperature, 2 cc. of this solution into a 

 comparison tube. Add 25 cc. of the aldehyde-free alcohol (previously cooled to 

 14°-16°C.), then 20 cc. of the sulphite-fuchsin solution (also cooled) and finally make 

 up to the 50 cc. mark with more aldehyde-free alcohol. Mix thoroughly, stopper 

 and keep at 14°-16°C. for 15 minutes. Prepare a standard for comparison at the 

 same time and in the same manner, using 2 cc. of the standard citral solution, and 

 compare the colors developed. Calculate the amount of citral present and re- 

 peat the determination, using a quantity sufficient to give the sample approxi- 

 mately the strength of the standard. From this result calculate the amount of 

 citral in the sample. If the comparisons are made in Nessler tubes, standards 

 containing 1, 1.5, 2, 2.5, 3, 3.5, and 4 mg. of citral, may be prepared and the trial 

 comparison made against these, the final comparison being made with standards 

 lying between 1.5 and 2.5 mg. with 0.25 mg. increments. 



It is absolutely essential to keep the reagents and comparison tubes at the re- 

 quired temperature, U^-IO'C. Where the comparisons are made in a bath (this being 

 possible only where the bath is of glass), the standards should be discarded within 

 25 minutes after adding the sulphite-fuchsin solution. Give samples and standards 

 identical treatment. 



Hiltner Method^. — Tentative. 



24 REAGENTS. 



(a) Meta-phenylendia/mn hydrochlorid solution. — Prepare a 1% solution of meta- 

 phenylendiamin hydrochlorid in 95% alcohol by volume. Decolorize, if neces- 

 sary, by shaking with fuller's earth and filter through a double filter. The solution 

 should be bright and clear, free from suspended matter, and practically colorless. 

 Prepare this solution only for immediate use. 



(b) Alcohol. — For the analj^sis of lemon extracts, 90-95% alcohol by volume 

 should be used, but for terpeneless extracts, 40-50*^0 alcohol by volume is sufficient. 

 Filter to remove any suspended matter. The alcohol need not be purified from 

 aldehyde. If not practically colorless, render slightly alkaline with sodium hydroxid 

 and distil. 



25 ' DETERMINATICX. 



All of the operations may be carried on at room temperature. Weigh 25 grams 

 of the extract into a 50 cc. graduated flask and make up to the mark with alcohol. 



