18 



precipitate be of a reddish color, dissolve it in a few drops of sulphuric acid, and add ferrous 

 sulphate and ammonia as before. As soon as a dark-colored or greenish precipitate has 

 been obtained, introduce 5 cc of alcohol, dissolve the precipitate in sulphuric acid, and shake 

 the fluid well and filter. In the absence of abrastol this method gives a colorless or light- 

 yellow liquid, while a red color is produced in the presence of 0.01 gram of abrastol. 



(b) SANGLE-FERRIERE'S METHOD, a 



Boil 200 cc of the sample with 8 cc of concentrated hydrochloric acid for one hour in a 

 flask with a reflux condenser attached. Abrastol is thus converted into beta-naphthol and 

 is detected as directed under "9." 



11. SUCROL OR DULCIN. 



(a) MORPURGO'S METHOD, b 



Evaporate about 1QO cc of the sample (or of the aqueous extract prepared as directed on 

 page 3) to a sirupy consistency after the addition of about 5 grams of lead carbonate, and 

 extract the residue several times with alcohol of about 90 per cent; evaporate the alcoholic 

 extract to dryness; extract the residue with ether, and allow the ether to evaporate spon- 

 taneously in a porcelain dish. Now add 2 or 3 drops each of phenol and concentrated sul- 

 phuric acid and heat for about five minutes on the water bath; cool; transfer to a test tube 

 and pour ammonia or sodium hydroxid over the surface with the least possible mixing. The 

 presence of dulcin is indicated by the formation of a blue zone at the plane of contact. 



(b) JORISSEN'S METHOD, c 



Suspend the residue from the ether extract obtained as directed above in about 5 cc of 

 water; add from 2 to 4 cc of an approximately 10 per cent solution of mercuric nitrate, and 

 heat from five to ten minutes on the water bath. In the presence of sucrol a violet-blue 

 color is formed, which is changed to a deep violet by the addition of lead peroxid. 



a Comp. rend., 1893, 117: 93. b Zts. anal. Chem., 1896, 35: 104. c ibid., p. 628. 



O 



