102 



The results reported are tabulated as follows: 



Results obtained in the cooperative work on an acetanilid mixture. 



o Reported by J. P. Street. 



& In cases where two percentages for volumetic and gravimetic determinations of the same substance \ve; e 

 reported, the mean of such percentages has been taken in computing the total percentage. 



Owing to an ambiguity in the expression "dilute sulphuric acid" employed in the 

 method under caffein, as also in the footnote a, page 100, for standard bromid-bromate 

 solution, some of the workers quite naturally used the pharmacopoeial strength, 

 with the result that the acetanilid was not completely hydrolyzed. This undoubtedly 

 explains the somewhat high results for caffein and the correspondingly low ones for 

 acetanilid. The strength of acid intended and the one actually employed ior this 

 purpose in the Bureau of Chemistry is that ordinarily used in laboratory work and 

 is made by diluting 1 part of concentrated sulphuric acid (whose specific gravity is 

 not less than 1.826 at 25) with 5 parts of water. From two to three hours' heating on 

 the steam bath is usually required to completely hydrolyze the acetanilid. 



Notwithstanding this ambiguity the results obtained are very gratifying, in view 

 of the fact that the method is new and the workers have entered into a comparatively 

 new field. The percentages of variation are so small as to almost warrant the referee 

 in recommending it as a provisional method to the association. He believes, how- 

 ever, that the method should receive additional study, and so recommends. It is 

 also recommended that additional mixtures be tested with this and such other methods 

 as may be found desirable. 



