30 BULLETIN 1390, U. S. DEPARTMENT OF AGRICULTURE 
REDUCTION AND STEAM DISTILLATION 
Proceed as directed in the first paragraph under reduction and 
extraction. Then steam distil the alkaline mixture until no more 
oil is carried over. Separate the oil layer and extract the water 
layer with two 150 c. c. portions of ether. Add the extracts to 
the oil layer and wash the mixture with successive 10 ¢. ¢. portions 
of water until the alkali and salts are removed. Complete the 
determination as directed under reduction and extraction, beginning 
with ‘“EKvaporate the solvent on the steam bath.” 
ISOMERIC AND SIMILAR DYES IN AMARANTH 
Take that volume of the master solution which contains 0.1 gram 
of the dye and dilute, if necessary, to 40 c. c. with water. Add 
10 c. c. of 0.1 N benzidine solution (9.2 grams of base per liter in 
0.5 N hydrochloric acid), mix well, and let stand exactly two minutes. 
Filter through a fluted paper and dilute 10 c. c. of the filtrate to 
100 c. ce. Compare this solution colorimetrically with a standard 
amaranth solution containing 0.4 mg. of the dye per 100 ¢. c. The 
master solution of the amaranth to be tested may be used in making 
the standard solution. If, after the benzidine treatment, the solu- 
tion obtained is not more deeply colored than the standard solution, 
the proportion of isomeric dyes may be considered to be below 1.5 
per cent. 
SODIUM IODIDE 
For erythrosine.— Dilute to about 400 c. c. that volume of the master 
solution which contains 5 grams of the dye and add a mixture of 
2 c. ce. of strong nitric acid and 10 to 20 c. c. of water. Dilute to 
exactly 500 c. c., mix, and filter through a dry paper. . Place 200 c. c. 
of the filtrate in a porcelain casserole and make slightly alkaline with 
10 per cent sodium hydroxide solution. Add about 20 c. c. of 7 per 
cent potassium permanganate, mix, and add 10. ¢. of strong nitric 
acid. Place on a steam bath and evaporate to dryness. Add 5c. c¢. 
of 7 per cent potassium permanganate and 5c.c. of strong 
nitric acid and again evaporate to dryness. Then add about 50 c. c. 
of water, 5c. c. of strong nitric acid, and 25 to 30 c. c. of a saturated 
solution of sulphur dioxide (p. 15). Stir frequently, Rees u 
any lumps, until the hydrated oxide of manganese is disso adh 
Filter, wash the paper with water, and add to the combined filtrate 
and washings an excess of 10 per cent silver nitrate solution. Boil 
until the sulphur dioxide has been expelled. When cool collect the 
silver iodide on a weighed Gooch crucible. Wash with hot water, 
dry, and weigh. Calculate as percentage of sodium iodide. 
IODINE ORGANICALLY COMBINED 
For erythrosine.—Place in a porcelain casserole that volume of the 
master solution which contains 0.3 to 0.4 gram of the dye. Add 5 
c. c. of a 10 per cent sodium hydroxide solution and 35 c. ¢. of a 7 per 
cent solution of pure potassium permanganate and mix. Partially 
cover the vessel with a watch glass and add 10 ¢. ¢. of strong nitric 
acid. Place on asteam bath and keep covered until spattering ceases. 
Remove and wash the watch glass and allowevaporation to proceed 
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