VINEGAR. 



21. Lead Acetate Precipitate. 



105 



Add a few drops of neutral lead acetate to 10 cc of a vinegar. Failure to 

 obtain a precipitate proves that it is not a cider vinegar. 



22. Detection of Foreign Pungent Materials. 



Exactly neutralize a portion of the vinegar (the residue from determination 

 of total acidity may be used), evaporate part of the water, and test the concen- 

 irntod solution by taste for pungent substances; agitate the liquid with ether 

 in a separatory funnel, remove and evaporate the ethereal layer, and taste 

 tiie residue. The identification of the specific substance is rarely possible. 



23. Heavy Metals. 



Evaporate from 200 to 500 cc to dryness. In case of cider, malt, and other 

 vinegars ri< h in solids, add a little sodium hydroxid and potassium nitrate and 

 incinerate. Dissolve the ash thus obtained, or the solids themselves, and pro- 

 11 coed as directed under " IX. Canned Vegetables," page 61. 



24. Detection of Preservatives. 

 Proceed as directed under " XXVII. Food Preservatives," page 179. 



