XXIX] DRUGS 355 



(b) Standard sodium thiosulphate solution. — Dissolve 30 grams of crystallized 

 sodium thiosulphate in water and dilute to 1 liter. Standardize this solution against 

 the purified iodin as follows: Weigh out about 0.3 gram of the purified iodin in a 

 small, glass capsule (about § inch high and f inch diameter), provided with a closely 

 fitting glass cap or stopper, and place the capsule in a 200 cc. Erlenmeyer flask con- 

 taining 0.5 gram of potassium iodid dissolved in 10 cc. of water. After complete 

 solution, titrate with the sodium thiosulphate solution, using 1 or 2 drops of starch 

 solution as an indicator. 



(C) Standard iodin solution. — Dissolve 40 grams of potassium iodid in the least 

 possible quantity of water, add 30 grams of the purified iodin and, after solution, 

 dilute to 1 liter. Standardize 25 cc. of this solution against the standard sodium 

 thiosulphate solution. 



12 DETERMINATIOxV. 



(1) Place 0.2 gram of the acetphenetidin-acetanilid mixture in a 50 cc. lipped 

 Erlenme3-er flask, add 2 cc. of glacial acetic acid, heat gently over a wire gauze to 

 complete solution and dilute with 40 cc. of water, previously warmed to 70°C. 

 Transfer the clear liquid with two 10 cc. portions of warm (40°C.) water to a glass- 

 stoppered, 100 cc. graduated flask containing 25 cc. of the standard iodin solution 

 warmed to 40°C. Stopper, mix thoroughly, then add 3 cc. of concentrated hydro- 

 chloric acid, continue shaking until crystallization begins and then set aside to 

 cool. If the ratio of acetphenetidin to acetanilid is equal to or greater than unity, 

 crystalline scales will form almost immediately on the addition of acid. As the 

 proportion of acetanilid increases, however, the periodid tends to remain in the liquid 

 state. In such cases, gentle agitation or rotation of the flask in water, warmed 

 not to exceed 40°C., hastens the formation of crystals. When the contents of the 

 flask are at room temperature, fill with water to within 2-3 cc. of the mark, mix 

 thoroughly and allow to stand overnight. Fill to the mark with water, mix thor- 

 oughly, allow to stand 30 minutes, filter through a 5.5 cm. dry, closely fitted filter 

 into a 50 cc. graduated flask, rejecting, however, about 15 cc. of the first runnings 

 but reserving them for the recovery of acetanilid. Transfer the 50 cc. aliquot to a 

 200 cc. Erlenmeyer flask and titrate with the standard sodium thiosulphate solution. 

 Calculate the amount of acetphenetidin from the following formula: 



Acetphenetidin = I (0.0896 X N) in which 



0.0S96 = the quantity of acetphenetidin contained in 1 cc. of a normal 

 solution of this substance; 

 N = the normality of the standard sodium thiosulphate solution 



employed; and 

 I = the number of cc. of the standard sodium thiosulphate solu- 

 tion corresponding to the iodin combined with the acet- 

 phenetidin. 



The formula of the precipitated periodid, which constitutes the basis for the above 

 determination, is (C>H50.C6ll4XH.COCH3)2HI.l4. 



(2) The gravimetric determination of acetphenetidin may, if desired, be efi"ected 

 as follows: Filter off the periodid, preferably by suction, wash with 10-15 cc. of the 

 standard iodin solution, then transfer together with the filter to a scparatory funnel, 

 using not over 50 cc. of water. Remove both free and added iodin with a few small 

 crystals of sodium sulphite and extract the liquid with three 50 cc. portions of 

 chloroform, washing each portion subsequently into a second separatory funnel with 

 5 cc. of water. After washing and clearing, filter the chloroform solution through 



