458 



FOODS. AND FOOD ADULTERANTS. 



The flask containing the cake of insoluble fat acids is inverted and 

 allowed to drain and dry for twelve Lours (Fig. 24 bis), together with 

 the filter paper through which its soluble fatty acids have been filtered. 

 When dry the cake is broken up and transferred to a weighed glass 

 evaporating dish. Remove from the dried filter paper as much of 

 the adhering fat acids as possible and then add them to the contents of 

 the dish. The funnel, with the filter paper, is then placed in an Erlen- 

 meyer flask, a hole is made in the bottom of the filter paper, and it is 

 thoroughly washed with absolute alcohol from a wash bottle. The flask 

 is rinsed with the washings from the filter paper and pure alcohol, and 

 these transferred to the evaporating dish. The dish is placed on the 

 steam-bath and the alcohol driven off. It is then transferred to the air 

 bath and dried at 100 C. for two hours, taken out, cooled in a desicca- 

 tor, and weighed. It is then again placed in the air-bath and dried for 

 another two hours, cooled as before, and weighed. If there is no con- 

 siderable decrease in weight the first weight will do 5 otherwise, re- 

 heat two hours and weigh. This gives the weight of insoluble fat acids 

 in the quantity taken, from which the percentage is easily calculated. 



Table for the calculation of soluble fatty acids. 



The table gives the weight of soluble acids (butyric, etc.) for each 

 quarter of a cubic centimeter of deci-normal alkali from 10 to 30. 



