356 METHODS OF ANALYSIS [Chap. 



a dry 5.5 cm. filter into a 200 cc. Erlenmeyer flask, distil off most of the chloro- 

 form, transfer the residual solution (5-10 cc), by means of a little chloroform, to 

 a small, tared beaker or crystallizing dish, evaporate to dryness on a steam bath, 

 cool and weigh. 



For the identification of acetphenetidin, either alone or in admixture with acet- 

 anilid, the following test will be found of value': To 1-2 mg. of the sample in a test 

 tube add a drop of acetic acid, 0.5 cc. of water and 1 cc. of N/10 iodin, warm the 

 mixture to about 40°C., then add a drop of concentrated hydrochloric acid. If 

 acetphenetidin alone is present, its periodid separates almost immediately in the 

 form of reddish brown leaflets or needle-like crystals. If the sample consists largely 

 of acetanilid, the separation takes place on cooling and shaking the liquid. In the 

 presence of considerable acetanilid, the periodid first separates as minute, oily 

 globules, which, on vigorous shaking, gradually become crystalline. This test is so 

 delicate that as little as 0.5 mg. of acetphenetidin may, if alone, be detected in 

 the form of its characteristic periodid. 



13 ACETANILID.-TENTATIVE. 



(1) If the combined weight of the acetphenetidin-acetanilid mixture is known, 

 determine that of the latter ingredient by difference; or, (2) Determine it directly 

 from a second aliquot of the filtrate from the acetphenetidin periodid in 1 2 as follows : 



Pipette 25-30 cc. of the clear liquid into a separatory funnel, decolorize with 

 solid sodium sulphite and solid sodium bicarbonate in slight excess, add 1 or 2 drops 

 of acetic anhydrid, then extract with three 60 cc. portions of chloroform, passing 

 the chloroform solution, when cleared, through a small, dry filter into a 200 cc. 

 Erlenmeyer flask, and distil the chloroform, by the aid of gentle heat, to about 20 

 cc. Add 10 cc. of sulphuric acid (1 to 10) and digest on a steam bath until the resi- 

 due has been reduced one half, add 20 cc. of water and continue the digestion for 

 an hour; then add a second 20 cc. portion of water and 10 cc. of concentrated hydro- 

 chloric acid, titrate very slowly, drop by drop, with the standard bromid-bromate solu- 

 tion, 2 (a), until a faint j^ellow color remains. While adding this reagent, rotate 

 the flask sufficiently to agglomerate the precipitated tribromanilin. Calculate the 

 amount of acetanilid present. 



If the preparation contains caffein or antipyrin or both in addition to acet- 

 anilid and acetphenetidin, proceed as follows :'(!) Digest the mixture by heating 

 with dilute sulphuric acid to convert acetphenetidin and acetanilid to phenetidin 

 and anilin sulphates, respectively; (2) Separate the caffein and antipyrin by ex- 

 traction with chloroform; (3) Re-form acetphenetidin and acetanilid by treat- 

 ing the solution of the corresponding sulphates with solid sodium bicarbonate in 

 slight excess, then add a few drops of acetic anhydrid and extract with chloroform*. 



Acetphenetidin CPhenacetin) and Salol in Mixtures^ 

 acetphenetidin. 

 14 Acid Hydrolysis Method. — Tentative. 



Weigh out on a tared 5.5 cm. filter" an amount of the sample equal to, or a mul- 

 tiple of, the average weight of a unit dose and wash with suflScient successive, small 

 portions of chloroform to extract completely all acetphenetidin and salol present 

 in the mixture (about 40 cc). Collect the solution in a tared, 100 cc. beaker and 

 evaporate on a warm plate (50°-60°C.) to apparent dryness, using an air blast. 

 Let stand 24 hours at room temperature to practically constant weight, then trans- 

 fer the crystalline residue, by means of chloroform, to a 50 cc. lipped Erlenmeyer 

 flask, evaporate the solvent by means of an air blast and gentle heat, add 10 cc. 



