FOOD PRESERVATIVES. 109 



tube connecting the flask with condenser should be very short, with an inside diam- 

 eter of not less than f inch, and should turn into the condenser immediately above 

 the stopper in flask. Conduct steam through a small tube passing through the stop- 

 per and dipping deeply into the material in the flask. Submerge the distilling flask 

 almost to the stopper in a linseed oil bath and distill with temperature of the oil at 

 from 120 to 130 C. 



Care must be taken not to let the contents of the flask get too low, as the heat will 

 decompose the organic matter. The temperature in the flask will go but little above 

 100 C. unless the solution in the flask is allowed to get too low. 



Distill off 500 cc to 600 cc, acidify with dilute sulphuric acid, extract with about 

 30 cc of chloroform or ether, and proceed as directed above. 



(a) SACCHARIN. 



If the solution for saccharin and salicylic acid has an intensely sweet taste, it is an 

 indication of saccharin. If it is sweet, dilute a portion of it about ten times, and 

 taste again. (See also page 51.) 



(b) SALICYLIC ACID. 



(1) First method.* 



Place a few drops of solution for salicylic acid in a porcelain dish, add 2 or 3 drops 

 of ferric chlorid solution in such a way that the solutions will come together slowly, 

 which will give a purple or violet color if salicylic acid is present. 



(2) Second method.* 



Place about 0.5 cc of the solution in a porcelain dish and evaporate to dry ness at a 

 low temperature Warm the'residue carefully with one drop of concentrated nitric 

 acid, and add 2 or 3 drops of ammonia until alkaline. The presence of salicylic acid 

 is indicated by the formation of a yellow color of ammonium picrate, and maybe 

 confirmed by dyeing a thread of fut-1'ivc wool in it. 



4. DKTWTION OK I'.KN/OH Ann. 1 ' 



Separate benzole acid by extraction or distillation as directed under salicylic acid, 

 and test by one of the following methods: 



(1) Firxf nnihod. c 



Divide solution for benzoicaci<l into three portions and examine one portion by 

 each of the following methods: Make alkaline with ammonium hydroxid, expel the 

 excess of ammonia by evaporation, take up the residue with water, and add a few- 

 drops of a neutral 0.5 per cent solution of ferric chlorid. The presence of benzole 

 acid will be indicated by the formation of a brownish-colored precipitate of ferric 

 benzoate. 



(2) &;'ui,,l untkod. c 



Kvaporate to dry ness and treat the residue with 2 or 3 cc of strong sulphuric acid, 

 Heat till white fumes appear; organic matter is charred and benzoicacid is converted 

 into sulpho-benzoic acid. A few crystals of potassium nitrate are then added. This 

 causes the formation of metadinitrobenzoic acid. When cool, the acid is diluted 

 with water and ammonia added in excess, followed by a drop or two of ammonium 



U. S. Dept. of Agr., Div. of Chem., Bui. 51, p. 132. 

 b See also Appendix, page 160. 

 Bui. Soc. Chini. 1890 [3] , 3, 414. 



