EXAMINATION O^ THE FATS. IS 



paper must be of the best quality and so dense that even 

 hot water will only percolate through it drop by drop. 

 Weigh a small beaker, a funnel, and also the funnel plus 

 the filter. In this way one may get the weight of the 

 filter plus the beaker. (The hardened filters made by 

 Schleicher & SchuU are especially adapted to this work.) 



The weighed filter is pressed tightly into the funnel 

 and thoroughly moistened and half filled with water. 

 Then pour out of the evaporator the watery fluid and the 

 molten fat, and wash the dish and glass rod with boiling 

 water. It is not difificult to transfer all of the oily mass 

 to the filter, so that there need not be a trace remaining 

 on the dish. To be certain, one may wash the dish with 

 ether and afterwards add the material thus recovered to 

 the insoluble acids. As a rule the amount recovered 

 from the dish with ether in this way is very small, usu- 

 ally less than one milligram. 



The fatty-acids are now very carefully washed on the 

 filter with boiling water. Never fill the funnel more 

 tiian two-thirds full. When the filtrate tested with sensi- 

 tive litmus paper no longer reacts acid (three grams of 

 fat usually require three-fourths of a litre of boiling 

 water), allow the water to drain out and then dip the 

 funnel and contents into a beaker filled with cold water 

 so that the surface of the water is the same within as 

 inoiniAV As soon as the contents of the filter beconie> 

 solidified, it is removed from the funnel and placed in the 

 weighed beaker and dried to constant weight in a water 

 oven. 



Instead of estimating the insoluble acids as just de- 

 scribed, E. Reichert estimates the volatile fatty-acids and 

 recommends the following method for the purpose :* 



Two and one-half grams of purified water-free fat, pre- 

 viously filtered through cotton, are placed, in a fluid 



♦Zeitsch. f. Analyt. Chem. XVIII. 68. 



