210 EXPERIMENT STATION EECORD. 



volatile acids were determined. Tlie viscosimeter devised by one of the authors 

 and Bingham, with some modifications, was used in the investigation. 



" Oleomargarine fats are always more viscous than butter fats except, of 

 course, where the viscosity of the former is greatly lowered by the introduction 

 of large amounts of liquid fats as indicated by a chemical analysis. On stand- 

 ing, the viscosity of butter probably increases to a maximum due to a loss of 

 volatile acids, and then becomes less viscous as putrefaction sets in. 



"Although the viscosities for both fats vary somewhat in products from 

 different soui'ces, the fluctuation is always about a mean value which might be 

 assumed without great error as a standard. The viscosities of the mixtures 

 are not strictly additive. The fluidities are practically linear functions of the 

 temperature. The fluidities of the mixtures are additive, so that these, and 

 not viscosities, should be the basis for any comparison. 



"Assuming that the fluidity of butter does not vary more than 5 per cent in 

 value, an adulteration of 10 per cent oleomargarine can be detected with as- 

 surance." 



The detection of gelatin in sour cream, A. Seidenbeeg {Jour. Indus, and 

 Engin. Chem., 5 (.1913), No. 11, pp. 927, 928).— The usual method for detecting 

 gelatin in milk and cream consists in removing the proteins with acid mercuric 

 nitrate and the precipitation of the gelatin in the filtrate with picric acid. It 

 often occurs, however, that with a sweet cream no precipitate is noted. " It 

 has been frequently noticed that a sweet cream which gave no precipitate with 

 picric acid would, after souring, show quite a perceptible tui'bidity on its addi- 

 tion, often heavy enough to lead to the assumption that gelatin was present. 

 It seems most probable that this is due to protein decomposition products not 

 precipitated by the acid mercuric nitrate." 



The picric acid precipitate from sour cream is flocculent and settles quite 

 rapidly, while that due to gelatin is small and granular and on shaking in the 

 tube will coalesce in large lumps and leave the solution almost clear. A marked 

 difference was found between the precipitates as regards solubility in hot, 

 neutral water ; only the gelatin picrate is soluble in hot water. 



A modiflcatiou of the Official Method based on these findings is presented. 



Sampling" ice cream, J. O. Halverson {Jour. Indus, and Engin. Chem., 5 

 {1913), No. 5, pp. 409, JflO). — It is shown that ice cream, as a rule, is not uni- 

 form in composition throughout the can, although this may not be noticeable 

 except on the paddles of the freezer. 



" In taking charges from preserved ice cream samples which have stood in a 

 cooler so that the cream rises, perfectly uniform charges can not be obtained. 

 This, it appears, causes a slightly greater variation in the fat reading with a 

 tendency to run somewhat lower. The mixing of ice cream samples should be 

 carefully performed, especially when they have stood so that the cream has 

 risen to the top." 



The modified Babcock for fat in sweetened dairy products — ice cream, J. O. 

 Halverson {Jour. Indm. and Engin. Chem., 5 {1913), No. 5, pp. 403-^09, figs. 

 2). — It is stated that the Babcock and the Adams-Soxhlet methods can not be 

 used for determining fat in ice cream. The same is true of the modifications 

 of the Babcock test, e. g. that of Leach and Farrington, used for sweetened 

 condensed milk. Various volumetric and gravimetric methods (Rose-Gottlieb 

 and Paul's gravimetric methods and Holm's and Howard's volumetric methods) 

 suggested for this purpose are also deemed unsatisfactory, and the following 

 modification of the Babcock method is proposed : 



"To an 18 gni. charge add the usual sulphuric acid (specific gravity 1.82 to 

 1.83) in small portions of 3 cc. at a time, shaking after each addition with a 

 slight pause. Continue adding acid in portions until a light amber brown color 



