FOOD PRESERVATIVES. 



189 



formed). Decant the amyl alcohol, filter If turbid, and evaporate to dryness. 

 Add to the residue 2 cc of a mixture of equal parts of strong nitric acid and 

 water, heat on the water bath until half of the water is evaporated, and trans- 

 fer to a test tube with the addition of 1 cc of water. Add about 0.2 cc of ferrous 

 sulphate and an excess of ammonium hydroxid. drop by drop, with constant 

 shaking. If the resultant precipitate is of a reddish color, dissolve it in a few 

 drops of sulphuric acid, and add ferrous sulphate and ammonium hydroxid 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 color- 

 less or light-yellow liquid, while a red color is produced in the presence of 

 0.01 gram of abrastol. 



(b) SANGLE-FERRIERE'S METHODS 



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 section 9, page 188. 



11. Sucrol or Dulcin. 

 (a) MORPURGO'S METHOD.* 



Evaporate about 100 cc of the sample (or of the aqueous extract prepared 

 as directed on page 179) 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 alcohol extract to dryness; extract the 

 residue with ether, and allow the ether to evaporate spontaneously in a porce- 

 lain dish. Add 2 or 3 drops each of phenol and concentrated sulphuric acid 

 and heat for about 5 minutes on the water bath ; cool ; transfer to a test 

 tube and pour ammonium hydroxid or sodium hydroxid over the surface with 

 the least possible mixing. The presence of dulcin is indicated by formation 

 of a blue zone at the plane of contact. 



(b) JORISSEN'S METHODS 



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 solu- 

 tion of mercuric nitrate, and heat from 5 to 10 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. 



Comp. rend., 1898, 117: 7!M. & Zts. anal. Cbem., 1896, 86: 104. 



Ibid., p. 628. 



