38 ADULTERATED DRUGS AND CHEMICALS. 



and heat the mixture for four hours at 150 C. On diluting the result- 

 ing solution with three parts of water the phenacetin separates out in 

 fairly pure crystals. This appears to be the method now used in the 

 manufacture of phenacetin. 



The chemical constitution of phenacetin can readily be made out 

 from what has been said above. Its chemical names are p-acetainino- 

 phenol ethyl ether, p-acetphenetidin, p-acetamidophenetol, ethoxy- 

 acetanilid, and oxyethy lacetanilid. The last two names show their close 

 relation to acetanilid. This is also shown by the following formulae: 



<NHC 2 H 3 O 

 (phenacetin). 

 OC 2 H 5 



These two compounds resemble each other not only in chemical 

 constitution, but also in their physical properties. 



PHYSICAL AND CHEMICAL TESTS. 



THE MELTING POINT. 



Many and varied have been the tests proposed for establishing the 

 purity of phenacetin, but at present the most reliable is its melting 

 point, which is near 135 C. This important constant is disturbed by 

 the presence of any impurity, such as unconverted p-phenetidin, ace- 

 tanilid, antip} T rin, salicylic acid, quinine sulphate, starch, milk sugar, 

 etc. All powders so far examined in this laboratory having a melting 

 point within 1 degree of normal have deported themselves in every 

 respect like pure phenacetin. 



The presence of unconverted p-phenetidin a in phenacetin is detected 

 by melting 2.5 grams of pure crystal chloral hydrate in a test tube on 

 a water bath, then adding 0.5 gram of phenacetin, and continuing the 

 heating for a short time. If the phenacetin is pure, only a pinkish 

 color develops on prolonged heating, whereas the presence of p-phene- 

 tidin (p-amido-phenetol) gives within five minutes an intensely red or 

 reddish-violet coloration. * 



The one adulterant of phenacetin which appears to be difficult of 

 detection is acetanilid. Its influence on the melting point of phenace- 

 tin was noted by E. Utescher, 6 who found that phenacetin mixed with 

 5 per cent of acetanilid shows, at from 113 to 114 C., minute drops 

 of liquid on the sides of the capillary tube and melts completely at 

 from 127 to 128 C. H. Schweitzer c studied the melting points of 

 various mixtures of phenacetin and acetanilid and observed the strange 

 phenomenon that all mixtures of these two chemicals began to melt at 

 92 C. Neither phenacetin nor acetanilid shows the least change at 



Pharm. Ztg., 1891, 86: 185, through J. Soc. Chem. Ind., 10: 799. 

 &Apoth. Ztg., 1888, 8: 483, through Ztschr. anal. Chem., 27: 666. 

 c J. Soc. Chem. Ind., 1895, 14: 852. 



