102 GIBBS. 



acids, have been found by the writer and otlicr investigators in soda-water 

 flavors, root beers, sarsaparillas and cod-liver oil emulsions, both when 

 meth^'l salicylate was present and absent, and several manufacturers have 

 verified the findings by submitting their fomiulas for some of these prep- 

 arations. In many eases it is possible that a preservative, in addition 

 to the methyl salicylate, is quite supei-fluous, the ester probably having 

 antiseptic qualities ^ sufficient to render the employment of other steriliz- 

 ing agents or processes unnecessary. 



Concerning the second source of salicylic acid, namely, as an impurity 

 in the methyl salicylate, an examination of all of the different samples 

 available in this laboratory and in the city of Manila, eight in all, has 

 revealed the presence of tlie free acid in every case. Two of these samples 

 were represented to be genuine oil of gaultheria, and six were s}Tithetic 

 preparations. All were of European exportation and had been in stock 

 in this city from a few days to over a year. The amounts of free salicylic 

 acid varied from a trace in one laboratory sample to 0.02.5 per cent by 

 weight in a genuine oil of wintergreen. These small amounts do not 

 wholly account for the larger quantities of salicylic acid or its salts 

 which have been found in a number of different preparations upon the 

 local markets and entering the port of Manila. 



The third source, namelj', the li3rdrolysis of the ester, will be sho\vn * 

 to account, in many cases, for the presence of free salicylic acid in prep- 

 arations in which comparatively pure methyl salicylate has been employed 

 as. an ingredient. With allvalies the rate of hydrolysis is very rapid; it 

 is slower with acids, and even with distilled water the hydrolysis is 

 measurable. The temiDerature is an imijortant factor of the rate. It 

 is' therefore not surprising that the formation of salicylic acid from 

 methyl salicylate in this way is quite appreciable in foods or drugs which 

 have been shipped by vessels to this port. The temperature of the holds 

 of the vessels often rises above 30° in the tropics. The voyage by fastest 

 steamers from Europe or the United States occupies about one month 

 and by sailing vessels a number of months, and during the entire voyage 

 the rolling and pitching of the vessel produces a constant agitation of 

 the contents of bottles, casks and other containers, maintaining, in all, 

 favorable conditions for hydrolysis. 



THE DETEBMINATION OF SALICYLIC ACID IN METHYL SALICYLATE. 



The free acid can be titrated directly. The indicators which have 

 been found to be applicable are Congo red an.d erythrosin. Alfred J. 

 Cohn ° says, "Congo red may be used for estimating mineral acids in the 



^ It is hoped that this investigation will form a part of a later paper. 

 ' While this phase of the question will be touched upon here, it will be further 

 dealt with in a later paper. 



'Indicators and Test Papers, J. Wiley & Sons, New York (1904), 56. 



