CONVEiSTTION OF OFFICIAL AGKICULTURAL CHEMISTS. 439 



the Hiibl method, 1.2 l)y the IlaiuiH luetliod, and 1.7 ]>> the Wijs nietliod.' The 

 maxiimuu differences were, i-espectively, 3.3, 1.9, and 2.8. 



In the extended investigations of tl\e associate referee comiJarative tests were made 

 of the Wijs sohition of iodin monochlorid in glacial acetic acid, tlie Hanus solution 

 of iodin monobromid in glacial acetic acid, and the Mcllhiney solution of l)romin in 

 carbon tetrachlorid. The objects in testing the Wijs and Hanus solutions were to 

 determine the excess of reagent necessary, the length of time required, and the effect 

 of light on the reaction. In tests on linseed oil an excess of the AVijs solution of 37 

 per cent gave the same results in 30 minutes as an excess of 62 per cent. An excess 

 of the Hanus solution of about 70 per cent was found necessary to insure complete 

 absorption in that time. Neither solution was appreciably affected by light in 30 

 minutes. It required 30 minutes with the Hanus solution to reach the constant 

 stage reached by the Wijs solution in lOnunutes, after which the absorption was con- 

 stant in both cases to the end of one hour, when a gradual rise occurred. 



Tests were also made of the bromin solution and of the substitution of carbon tet- 

 rachlorid for acetic acid in the preparation of the Hanus and Wijs solutions. It was 

 shown that good results could be obtained by the bromin solution only with dry 

 reagents and in the dark, and furthermore, that the figures could not be compared 

 with those of other methods. While solutions of iodin monochlorid and iodin mono- 

 bromid in carbon tetrachlorid gave more reliable results, their use was also considered 

 unsatisfactory for ordinary purposes. 



Work on the Dalican titer test was carried on with the cooperation of the chemists 

 of a number of packing houses. The detailed report upon this work was presented 

 as preliminary. The larger number of chemists cooperating used practically the 

 same modification of the Dalican test which was described. Particular attention 

 was paid to the effect of the two methods of saponification in use, the use of tubes 

 and air baths of different sizes, and the results obtained by different methods of 

 stirring. The need of a uniforni method of procedure was considered evident from 

 the work so far done. 



The associate referee recommended the adoption of the Hanus metiiod in place of 

 the Hiibl method, a change in the official method for determining the index of 

 refraction of oils and fats, as regards the factor used in the correction for temperature, 

 and certain changes in the provisional methods as regards Halpen's test for cotton- 

 seed oil, and Renard's test for peanut oil. 



Report of associate referee on dairy products, A. E. Leach. — The associate 

 referee gave several methods to supplement those already int-luded in the provisional 

 methods of the Association for the analysis of foods, and recommended their adoption 

 as i)rovisional methods. These methods relate to the detection of formaldehyde, 

 benzoic acid, and salicylic acid in milk; the detection of annatto in ))utter; the detec- 

 tion of azo dyes and annatto in oleomargarine; the detection of boric acid in butter; 

 the determination of fat in cheese, and the analysis of condensed milk. 



Report of associate referee on preservatives, W. D. Bigelow. — It was reported 

 that no definite results had l^een obtained. No field in connection with food chem- 

 istry was considered to be more in need of study than the determination of preserv- 

 atives. It was thought that in the near future it would be important to determine 

 the amount of preservatives present in foods, and the methods suggested for this pur- 

 pose were considered inadequate. During the year considerable attention was given 

 to qualitative methods for the detection of formaldehyde and quantitative methods 

 for the determination of salicylic acid and benzoic acid, the intention being to con- 

 tinue this work during the coming year. The referee requested as full collaboration 

 as possible. 



The determination of commercial glucose in some saccharine products, A. 

 E. Leach. — The determination of commercial glucose in such products as honey, 



