352 METHODS OP ANALYSIS [Chap. 



(C) Wagner's reagent. — Dissolve 2 grams of iodin and 6 of potassium iodid in a 

 minimum amount of water and dilute to 100 cc. 



3 CAFFEIN.— TENTATIVE. 



Treat the chloroform extract, obtained inl, with 10 cc. of sulphuric acid (1 to 

 10) and digest on a steam bath until the contents of the flask are reduced to 5 cc. 

 Add 10 cc. of water and continue the digestion until the liquid is again reduced to 

 5 cc, then cool and transfer to a separatory funnel with a minimum of water, so 

 that the final volume does not greatly exceed 20 cc. Add 50 cc. of the chloroform, 

 extract in the usual way and, after clearing, withdraw the lower layer through a 

 small, dry filter into a 200 cc. Erlenmeyer flask. Repeat the extraction with two 

 50 cc. portions of the chloroform. On the completion of the third extraction, 

 distil the combined extracts down to about 10 cc, finally transferring the residual 

 liquid, bj^ washing with chloroform, to a tared beaker or crystallizing dish. Allow 

 the solution to evaporate spontaneously, or by gentle heat and an air blast, to 

 apparent dryness. Cool and allow to stand until the weight becomes constant. 



Chloroform extracts in addition to caffein and acetanilid certain oils, fats, waxes, 

 resins, pigments and other substances from those preparations which contain pow- 

 dered cinnamon, celery seed, ginger or other vegetable products. These appear either 

 in suspension or solution after the caffein-acetanilid mixture has been digested and 

 contaminate the caffein. Remove any suspended impurities by filtering through 

 a small, moistened filter immediately after hydrolysis and prior to extraction with 

 chloroform. Should the recovered caffein be deeply colored or contaminated with 

 foreign matter, purify it as follows: Dissolve in very dilute sulphuric acid (about 

 5 cc of N/5 acid for every 100 mg. of caffein), filter, if necessary, through a mois- 

 tened filter, add 15-20 cc. of Wagner's reagent, sufficient at least to distinctly color 

 the supernatant liquid, stir and allow to stand an hour, preferably in a refrigerator. 

 Filter and wash the periodid with a few cc. of iodin solution, transfer both filter and 

 precipitate to a separatory funnel, using not more than 20 cc. of water, decolorize 

 with a crystal of sodium thiosulphate, then extract with three 50 cc. portions of 

 chloroform and proceed as directed above. 



4 ACETANILID.— TENTATIVE. 



Transfer the solution of anilin sulphate, remaining in the separatory funnel 

 in 3, to the Erlenmeyer flask used in effecting hydrolysis, then heat 10 minutes on 

 a steam bath to expel all traces of chloroform. Wash the filter, used in the pre- 

 ceding operation to dry the chloroform solution of caffein, with 5 cc. of water, 

 adding the latter to the main solution of anilin sulphate. Add 10 cc. of concen- 

 trated hydrochloric acid, then run in the standard bromid-bromate solution until 

 a faint yellow coloration remains, rotating the flask sufficiently to agglomerate the 

 precipitated tribromanilin. Calculate the quantity of acetanilid from the number 

 of cc. required to complete the precipitation. 



Caffein and acetanilid are the 2 principal ingredients of the preparation known 

 as "acetanilid compound", a further constituent being sodium bicarbonate. The 

 latter appears as the chloroform-insoluble residue and may be determined by ti- 

 trating such residue, or one obtained by titrating a portion of the original mixture, 

 with standard acid, using congo red as an indicator. The bicarbonate may also 

 be determined by igniting the original sample, or the chloroform-insoluble residue, 

 with sulphuric acid and weighing the resulting sodium sulphate. 



Should the "acetanilid compound" be combined with sodium bromid, the latter, 

 in the absence of other halides, may be determined volumetrically by the Volhard 

 method [III, 15]. 



