AGRICULTURAL CHEMISTRY AGROTECHNY. 809 



but to consider the case as a whole." It was found absolutely necessary to 

 follow the process exactly as described by the authors, particularly as regards 

 glycerol saponification. The method is probably of use in determining the 

 composition of margarin. 



A method for the determination of butter fat in ice cream, J. W. White 

 (Pennsylvania Sta. Rpt. 1910, pp. 2^3-2//7). — A method is proposed for using 

 the Babcock test in the determination of butter fat in ice cream, as follows : 



"Place the [Erlenmeyer] flask [containing the properly sampled ice cream] 

 into a bath of water heated to 80° F. and shake frequently by giving the flask 

 a gentle rotary motion until the contents assume the consistency of thin cream. 

 Pour the melted cream through a cream sampling sieve into a beaker, rubbing 

 through the fingers any lumps that may be left on the sieve ; pour several times 

 from one beaker to another until the sample is thoroughly mixed, and then 

 weigh out into a whole milk bottle while the sample is still warm, 6 gm. by 

 means of cream balances, and make the total volume up to 18 cc. Eight cc. 

 of oil of vitriol (specific gravity 1.83) are now added in 2 portions of 4 cc. each, 

 allowing about 2 minutes to elapse before the addition of the second portion 

 and mixing carefully the contents of the bottle after the addition of each por- 

 tion. The mixture at this stage should be of a light brown color and not 

 black as is the case with milk. If a black color is obtained, it is best to reject 

 the determination and weigh out a second portion, adding a smaller amount of 

 acid, because the sample contains little casein as compared with milk, and the 

 black color is due to the too violent action of the acid upon the sugar which it 

 chars and makes a clear reading very difficult. The bottle is now placed in 

 the steam tester and whirled for 3 minutes at the highest possible speed. 

 [Soft or] distilled water (150° F.) sufficient to bring the fat up to the base 

 of the neck is added. If any black particles are intermixed noticeably with 

 the fat, shake the bottle vigorously for a few seconds. Whirl again for 3 

 minutes as stated above, and add sufficient water, drop by drop, to bring the 

 fat column between the 10 per cent and the zero marks. Whirl the third time 

 for 2 minutes, and take the reading at 145° F. The resultant fat column should 

 be of a golden yellow color, free from any dark particles of charred sugar. 

 Multiply the reading by 3, as the bottle is graduated on a basis of 18 gm. 



" In reading the percentage of fat. the bottle should be held upright with the 

 graduated scale of the neck of the bottle on a level with the eye." 



The methods used for sampling and weighing the ice cream under examination 

 are also given. 



A new method for the determination of fat and fatty acids in feces, 

 O. FoLiN and A. H. Wentwokth (Jour. Biol. Chem., 7 (1910), No. 6, pp. 421- 

 426; gbs. in Zentbl. Physiol., 24 (1910), No. 21, pp. 976, 977).— The method is 

 as follows : 



One gm. of the dried and finely divided feces is packed into a piece of fat- 

 free filter paper, put in a thimble, placed in an extraction apparatus, and ex- 

 tracted with 150 cc. of water-free ether which has been previously saturated 

 with hydrochloric-acid gas. The ethereal fat solution (extract), which is con- 

 tained in a 250 cc. solution flask, is now distilled until nearly all of the ether 

 is driven off; then 50 cc. of petroleum ether (boiling point not over 60° C.) 

 ' is added, allowed to stand over night, filtered through cotton, the volatile por- 

 tion evaporated off, and the residue dried at 95° C. for 5 hours and weighed 

 as neutral fats and fatty acids. The residue is then dissolved in 50 cc. of 

 benzol, from 1 to 2 drops of alcoholic phenolphthalein is added, the solution 

 brought nearly to boiling, and immediately titrated with a volumetric solution 

 of sodium alcoholate (2.3 gm. of sodium in a liter of absolute alcohol). 



