of -ubstance u-ed should be such that the portion subsequently extracted with ether 

 will contain approximately 0.1 gram of sodium benzoate. The ether extract, after 

 washing \vith water, is allowed to evaporate to dryness spontaneously, or the first 

 portion of the ether may be distilled and recovered. After drying completely the 

 re.-idue is taken up with a small amount of absolute alcohol, for the purpose of sep- 

 arating interfering substances as far as possible, and filtered into a small beaker. 

 The alcohol is neutralized with sodium hydroxid, evaporated to dryness, and redis- 

 solved in a few cubic centimeters of alcohol saturated with silver benzoate. The 

 solution i- tillered if not clear, washed with a few drops of aldehyde-free alcohol, 

 saturated with silver ben/.oate, and treated with from 10 to 15 cc of a saturated solu- 

 tion of -ilver nitrate in aldehyde-free alcohol. The precipitate is collected in a 

 gooch, care beiiiLT taken that the asbestos filter be so constructed as to afford as rapid 

 filtration a- p<ible. The precipitate is then heated in a water-jacketed oven until 

 the ether is driven off, cooled, ami weighed. 



t are must be taken to perform all operations as quickly as possible in order to 

 prevent the separation of silver oxid. The aldehyde-free alcohol mentioned above 

 i- about 95 P-T <-cnt by volume, and is prepared according to the directions given 

 in Bulletin 107, page '.Mi, with the additional precaution of distilling over soda after 

 treatment with meta-phenylene-diamin hydrochlorid. This method involves the 

 u.-e of a on.-iderablr quantity of ether, which is objectionable because of its inflam- 

 mability and the tendency to di-.-olve sodium chlorid and other interfering substances. 

 Notwithstanding il> "iry results are rej>orted by Messrs. Hillyer and 



Flander- in the following table. No other results obtained by this method, using 

 ether as solvent, w. 1, though the precipitation of benzoic acid as silver ace- 



i>inu' chloroform as a pnlvrnt. was included in the work of several other eol- 





d tu silver benzntitt in tnnnttn kttctni i> (Hillyer and Flanders). 



o I>ast three results > K. T. FLmd.-r,; ..ttu-rs l,y \V. K. Hillyer. 



Tln->.' n -ulis were obtained by extra* tin- and pn-cipitating as silver benzoate in 

 the ether residue f..llowm- Method II as -iv.-n ..n page 70. The figures seem to be 

 in every way comparable with tho>e obtained by Method II (see p. 71). Extraction 

 withetherappear- to b- much less satisfactory than <-xtraction with chloroform, owing 

 to the removal of interfenn- .-ubstances by the solvent. These bodies are partially 

 removed by means of absolute alcohol, but this introduces an additional operation 

 ami the n-.-uli.- obtained are not as satisfactory as by extracting with chloroform from 

 a >olution saturated with sodium chlorid. In the table comparing Methods I and II 

 (p. 71 . i.- given the percentage of sodium benzoate precipitated as silver benzoate 

 from i he ,a Method II; that is, the liquid titrated under Method II was 



evaporated to dryness and us-l as a starting point for the silver benzoate method. 



In the following table are iim-n t he results obtained by the examination of a number 



of samples of commercial ken-hups using this method. In all cases the benzoic acid 



xtra. -ted by chloroform from a saturated sodium chlorid solution. Here, again, 



it will be aeen that the r.-sults obtained by weighing the residue are in all cases slightly 



