THE NEW YORK JOURNAL OF PHARMACY 



13 



a freshly prepared solution of ferric 

 chloride in water, o.i : loo, (c) petro- 

 leum ether of lowest possible boiling- 

 point, (d) 96 per cent, alcohol. 



Solutions required for comparison : 

 50 ccm. of the o.i : 100 salicylic acid 

 solution are placed in a mixing cylinder 

 having a capacity of 250 ccm, acidu- 

 lated with a few drops of sulphuric 

 acid, and shaken vigorously with 100 

 ccm. of petroleum ether, this being fol- 

 lowed by shaking again with 50 ccm. 

 of alcohol, the liquids then being al- 

 lowed to separate completely into lay- 

 ers. 0.5, i.o, 1.5. 2.0, 2.5 and 3 ccm. 

 (intermediary quantities can also be 

 taken) of the petroleum ether mixture, 

 are then mixed, in Eggert's tubes, each 

 with 10 ccm. of the ferric chloride solu- 

 tion, O.I : 100, and thoroughly shaken. 

 This results in transferring complete- 

 ly the salicylic acid contained in the 

 petroleum ether solution, to the aque- 

 ous layer containing the iron solution, 

 of course in the form of violet colored 

 ferric salicylate. 



The colors thus produced remain un- 

 changed for a period of at least 24 

 hours or longer, and thus these "Com- 

 parison" Solutions may be employed 

 for a number of determinations. 



Method of estimation : — 25 gm. of 

 the fruit juice or syrup to be examined 

 are placed in a mixing cylinder having 

 a capacity of 250 ccm. and water added 

 until the whole measures 50 ccm. Af- 

 ter acidulating with a few drops of 

 concentrated sulphuric acid, the mix- 

 ture is first shaken thoroughly with 

 100 ccm. of petroleum ether, and then 

 with 50 ccm. of alcohol, and then set 

 aside to layer, 



10 ccm. of the petroleum layer are 

 then mixed in an Eggert tube with 10 



ccm. of the aqueous iron chloride mix- 

 ture, thoroughly shaken, after which 

 the violet color produced is compared 

 with that of the solutions made for 

 comparison. 



If too deeply colored, a lesser quan- 

 tity of the petroleum ether solution, 5 

 ccm. or more or less must be used for 

 the experiment. If on the other hand 

 the violet color produced with 10 ccm. 

 of the petroleum ether solution is too 

 pale, more of the latter should be em- 

 ployed or added. It is recommended 

 that in such instances the petroleum 

 ether which has already been shaken 

 out, be removed by decantation, be- 

 fore adding the additional quantity. 



In this manner, by using smaller or 

 larger volumes of the petroleum ether 

 solutions of salicylic acid, as the case 

 may be, accurate determinations may 

 be made. 



If, after employment of the entire 

 100 cccm of the petroleum ether solu- 

 tion, a violet color is still absent, it 

 can with certainty be said the salicylic 

 acid has not been employed as a pres- 

 ervative, in the juice or syrup under 

 observation. 



Calculation: — The quantity of sali- 

 cylic acid present is a given sample of 

 juice or syrup is calculated after the 

 following formula : 



5 • c 



X = 



a . b 

 In this formula a = Quantity of 

 juice or syrup employed expressed in 

 grammes, b = Quantity of Petroleum 

 ether layer employed, expressed in 

 ccm. c = Quantity, expressed in ccm., 

 of the Petroleum ether layer used for 

 comparison, x = Quantity of Salicylic 

 Acid found. Example : 



