358 METHODS OF ANALYSIS [Chap. 



and pills, ascertain their average weight, powder in a mortar and weigh out an 

 amount of the powder equivalent to one or more tablets or pills for each determina- 

 tion prior to treatment in the separatory funnel. In the examination of alcoholic 

 preparations, distil off the alcohol from a measured volume on a steam bath, 

 transfer to a separatory funnel with a minimum of water and add sufficient solid 

 sodium bicarbonate (0.5 to 1.0 gram). 



19 ACETANILID.-TENTATIVE. 



Extract the alkaline solution, obtained under 18, with three 50 cc. portions of 

 chloroform, wash each portion with 5 cc. of water in a second separatory funnel 

 and collect the solvent, without previous drying, in a 200 cc. Erlenmeyer flask. 

 Designate the aqueous solution as A. Distil off the chloroform very gently to 

 about 5 cc, add 10 cc. of dilute sulphuric acid and completely hydrolyze on the 

 steam bath. Proceed from this point as directed in 4. 



20 SODIUM SALICYLATE.-TENTATIVE. 



Acidify the aqueous solution of sodiiun salicylate, A, under 19, with a few drops 

 of concentrated hydrochloric acid and extract with sufficient (3-5) 25 cc. portions 

 of chloroform to exhaust the salicylic acid present in the mixture. Treat each por- 

 tion in a second separatory funnel with 20 cc. of water, containing 1 gram of 

 anhydrous sodium carbonate for every 100 mg. of salicylic acid. Shake vigorously 

 and, after clearing, wash each portion again in a second separatory funnel with 5 cc. 

 of water, then add the washings to the main aqueous soda solution of sodium 

 salicylate. Dilute to a known volume, transfer an aliquot, representing about 100 

 mg. of salicylic acid, to a 200 cc. Erlenmeyer flask, make up to 100 cc, heat nearly 

 to boiling, then run in from a burette 25-40 cc. of strong (about N/5) iodin solu- 

 tion, sufficient to insure an excess during digestion and digest for an hour on a steam 

 bath. Remove the free iodin with a few drops of sodium thiosulphate solution, 

 decant the clear liquid through a tared Gooch, retaining most of the precipitate, 

 tetraiodophenylenquinon (C6H2l20)2, in the flask. To the latter add 50 cc. of 

 boiling water, digest 10 minutes on the steam bath, then filter, wash gradually 

 all the precipitate into a Gooch, using for this purpose and the final washing 

 about 200 cc. of hot water. Dry to constant weight in an air bath at 100°C. Mul- 

 tiply the weight of the precipitate by 0.4654 to obtain the quantity of sodium 

 salicylate present in the aliquot taken. 



Should the mixture contain caffein or antipyrin, or both, these substances will 

 appear with the acetanilid in the first chloroform extract and may be determined 

 as directed in the closely set type following 10. Should the acetanilid be replaced by 

 acetphenetidin in the mixture, the general procedure would not be materially altered, 

 the acetphenetidin being weighed directly after recovery from its washed chloro- 

 form solution as separated from the sodium salicylate. If, instead of sodium sal- 

 icylate, the mixture contains the free acid or its ammonium salt, add a larger quan- 

 tity of sodium bicarbonate prior to extraction with chloroform to insure the fixation 

 of salicylic acid. 



In the analysis of a mixture of caffein, acetanilid, sodium salicylate and codein 

 sulphate, the following procedure is recommended: (1) Extraction of caffein, acet- 

 anilid and salicylic acid from the acidified solution; (2) Washing the chloroform 

 solution with aqueous soda solution for the recovery of salicylic acid, preliminary 

 to its treatment with iodin solution; (3) Separation of caffein and acetanilid as 

 directed under 3 and 4; (4) Recovery of codein from the solution of its sulphate 

 after treatment with sodium bicarbonate and chloroform. 



