354 METHODS OF ANALYSIS [Chap. 



(b) In the case of alcoholic preparations, remove the alcohol from a measured 

 amount of the sample by heating on a steam bath. Extract the residue with three 

 50 cc. portions of chloroform in a separatory funnel. Distil off the greater por- 

 tion of the chloroform and evaporate the remainder on a steam bath. 



9 ANTIPYRIN.-TENTAXrVE. 



Transfer the residue, obtained in 8, which should weigh about 0.25 gram, to a 

 150 cc. separatory funnel by means of two 5 cc. portions of alcohol-free chloroform, 

 followed by 10 cc. of water. Add 1 gram of sodium bicarbonate and 10-15 cc. of 

 N/5 iodin (or double the quantity of N/10 iodin), adding the latter in small por- 

 tions and shaking the mixture vigorously after each addition. The iodin should 

 then be in excess of that required to convert all the antipyrin into the mono-iod 

 derivative. If not, add a little more and shake the mixture again. Remove the 

 free iodin with a small crystal of sodium thiosulphate, add 15 cc. of chloroform, 

 shaking vigorously for 1 minute. After clearing, draw off the chloroform solution 

 into a second separatory funnel, wash with 5 cc. of water, filter through a small, 

 dry filter into a tared 50 cc. beaker and evaporate to apparent dryness on the steam 

 bath, using an air blast. Repeat the extraction with two (three, if N/10 iodin is 

 used) 25 cc. portions of chloroform, wash, filter and evaporate each portion as 

 above. Dry the nearly colorless, crystalline residue of caffein and iodantipyrin 30 

 minutes at 105°C., cool and weigh. Designate this weight as "a". 



Dissolve the composite residue in 5 cc. of glacial acetic acid, add 10 cc. of 

 saturated sulphur dioxid solution, then transfer with hot water to a 400-500 

 cc. beaker until the final volume amounts to about 200 cc. Add sufficient silver 

 nitrate solution to precipitate all the iodin (about 0.3 gram of silver nitrate); then 

 a few drops of nitric acid, heat nearly to boiling and stir to agglomerate the silver 

 iodid. Add 15 cc. of concentrated nitric acid, cover the beaker with a watch glass 

 and boil gently for 5 minutes. Filter by decantation through a tared Gooch, wash 

 the precipitate once with a little alcohol, then with two 100 cc. portions of boiling 

 water and finally transfer the iodid to the crucible. Wash several times with hot 

 water and again with alcohol to remove traces of organic matter, dry 30 minutes 

 in an air bath at 110°C., cool and weigh. The weight of silver iodid multiplied by 

 0.8012 gives the weight of antipyrin. 



10 CAFFEIN.-TENTATIVE. 



Calculate the quantity of caffein by multiplying the weight of silver iodid by 

 1.3374 and subtracting the product from the weight "a" above. 



In the analysis of a mixture containing caffein, antipyrin, acetanilid and sodium 

 salicylate, the following steps are essential in effecting a separation: (1) Extraction 

 of caffein, acetanilid and antipyrin with chloroform from the aqueous soda solution; 

 (2) Hydrolysis with sulphuric acid of the 3 substances thus separated preliminary 

 to the determination of caffein and antipyrin as directed in 9 and 10. 



Acetanilid and Acetphenetidin (Phenacetinj in Mixtures', 

 acetphenetidin.— tentative. 



11 REAGENTS. 



(a) Purified iodin. — Dissolve 2 parts of resublimed iodin and 1 of potassiimi iodid 

 in 1 of water, pour the clear solution into a large volume of water, filter and wash 

 the finely precipitated iodin several times on a porous plate with water. Dry in 

 the air and finally in a desiccator over sulphuric acid where it is kept in a glass- 

 stoppered weighing bottle. 



