323] Estimation of Foreign Fats in Butter 193 



Melt up about 10 grams of butter in a beaker and filter 

 it. The easiest way of doing this is to place a filter funnel 

 with a short stem in the mouth of a 4-oz. conical flask, place 

 a paper in the funnel, and keep the whole arrangement in 

 a steam oven whilst the filtration proceeds. The fat is thus 

 kept fused, so that it runs through the filter, leaving the curd, 

 salt, and moisture behind. 



Weigh out accurately about 2 grams of the butter fat thus 

 prepared in an 8-oz. flask of the shape shown in fig. 11. 

 Add exactly 25 c.c. of the alcoholic potassium hydrate, and 

 warm on a water bath, shaking occasionally until saponifica- 

 tion is complete. Oily drops will remain on the surface of the 

 liquid until the reaction is ended. Whilst this is going on, 

 measure out another 25 c.c. of the alcoholic potash into a 

 clean flask. Add a drop of phenol-phthalein solution and 

 titrate with the seminormal acid. 



When the butter fat is completely dissolved, add a drop of 

 phenol-phthalein and run in the seminormal acid until the red 

 colour just disappears. Less acid will be required in this case, 

 as some of the potash will have been neutralised by the ' fatty 

 acids.' 



323. Calculation. — From the first titration one can 

 calculate the weight of potash in each c.c. of the alcoholic 

 potash solution. By subtracting the volume of acid required 

 after heating with butter fat from the volume required for 

 the 25 c.c. of original alcoholic potash, we may calculate the 

 quantity of alkali used by the butter. Knowing the weight of 

 butter fat used in the experiment, it is easy to find the number 

 of milligrams of potash required by each gram of butter. A 

 concrete example will make this plain : 



Weight of butter fat = 2*193 ; 



N 

 25 c.c. alcoholic KHO required 22-1 - HC1 ; 



