74 



The results obtained by this method are as follows: 



Determination of known amounts of benzoic acid in ketchups by Method III. 



An examination of this table shows that when there was present less than 0.15 

 gram of sodium benzoate no precipitate was formed, and in such cases as did give 

 a precipitate all results were from 0.1 to 0.15 gram low. This seemed to indicate 

 that there was something in the ketchup extract which held back the precipitation 

 and showed conclusively that the method could not be used for such materials in 

 combination with present extraction methods. 



It appeared probable that since the completeness of precipitation varied with 

 the alcoholic strength it might be interfered with by sugars, higher alcohols, oils 

 from spices, etc., and the following experiments were performed. The alcoholic 

 extract from 1 gram of spice was added to solutions containing 0.1 gram of sodium 

 benzoate and to blanks. Also 0.1 gram of sugar, glycerin, and dextrin were added 

 to similar solutions with the following results: 



Determination of sodium benzoate in the presence of spices, sugars, etc., by Method III. 



These figures show that it is the presence of the spices which causes the failure 

 of this method for the determination of benzoic acid in such products. It is pos- 

 sible that it may be applicable to other materials. 



PRECIPITATION AS SILVER BENZOATE (METHOD IV). 



This method was suggested and elaborated by Mr. W. E. Hillyer. 



The sample is extracted by means of ether as directed in Bulletin 107, page 179, 

 or by the method given by Dubois for the extraction of ketchups." The amount 



J. Amer. Them. Soc., 1906, 28: 1616. 



