X. FOOD PRESERVATIVES.— TENTATIVE. 



SALICYLIC ACID. 



1 PREPARATION OF SAMPLE. 



(a) Non-alcoholic liquids. — Many liquids may be extracted directly as described 

 in 2 or 4 without further treatment. If gums or mucilaginous substances are present, 

 pipette 100 cc. into a 250 cc. volumetric flask, add about 5 grams of sodium chlorid, 

 shake until the latter is dissolved, make up to the mark with alcohol, shake vigor- 

 ously, allow the mixture to stand for 10 minutes with occasional shaking, filter 

 through a dry folded filter and treat an aliquot of the filtrate as directed under (b). 



(b) Alcoholic liquids. — Make 200 cc. of the sample alkaline with sodium hydroxid 

 solution, using litmus as an indicator, and evaporate on a steam bath to about one 

 third its original volume. Dilute to the original volume with water and filter, if 

 necessary, through a dry filter. 



(C) Solid or semi-solid substances. — Grind the sample and mix thoroughly. Trans- 

 fer a convenient quantity (50-200 grams according to the consistency of the sam- 

 ple) to a 500 cc. volumetric flask, add sufficient water to make a volume of about 

 400 cc, shake until the mixture becomes uniform, add 2-5 grams of calcium chlorid, 

 shake until the latter is dissolved, render distinctly alkaline with sodium hydroxid 

 solution, using litmus as an indicator, fill to the mark with water, shake thoroughly, 

 allow to stand for at least 2 hours shaking frequently and filter through a large 

 folded filter. 



DETECTION AND ESTIMATION. 



2 Ferric Chlorid Test. — Qualitative. 



Introduce 50 cc. of the sample or an equivalent amount of an aqueous extract, 

 prepared as directed under 1 , into a separatory funnel, add one tenth its volume 

 of dilute hydrochloric acid (1 to 3) and extract with 50 cc. of ether. If the mixture 

 emulsifies, add 10-15 cc. of petroleum ether (b. p. below 60°C.) and shake. If this 

 treatment fails to break the emulsion whirl the mixture in a centrifuge, or allow it 

 to stand until a considerable portion of the aqueous layer has separated, run off 

 the latter, shake vigorously and again allow to separate. Wash the ether layer 

 with two 5 cc. portions of water, evaporate the greater portion of the ether in a por- 

 celain dish on a steam bath, allow the remainder to evaporate spontaneously and 

 add a drop of 0.5% ferric chlorid solution. A violet color indicates salicylic acid. 



If coloring matter or other interfering substances are present in the residue 

 left after evaporation of the ether, purify the salicylic acid by one of the following 

 methods: 



(a) Dissolve the residue from the ether extract, obtained as directed above, 

 in about 25 cc. of ether, transfer the latter to a separatory funnel and shake with 

 an equal quantity of water, made distinctly alkaline with several drops of am- 

 monium hydroxid. Allow to separate, filter the aqueous laj'er through a wet fil- 

 ter into a porcelain dish, evaporate almost to dryness, and test the residue as directed 

 above. 



(b) Drj' the residue from the ether extract, obtained as directed above, in a 

 desiccator over sulphuric acid and extract with several 10 cc. portions of carbon 



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