262 



THE CHEMICAL ANALYSIS OF BUTTER FAT. 



N 

 the acidity by titrating 2 c.c, with ^-r alkali and adding the 



figure thus obtained to the critical temperature. 



Crismer has shown that the critical temperature varies with 

 the percentage of insoluble fatty acids. Table XL VII. will show 

 the variations. 



TABLE XL VII. 



Butter usually has a critical temperature of 53 to 57 , and 

 in exceptional cases 59. 



The Reichert-Wollny figure may be calculated by the formula 



R-W = 129 critical temperature (with alcohol of sp. gr. 0-8195) 

 = 83-5 ,, ( absolute alcohol^. 



Valenta's Method Solubility in Acetic Acid/ Valenta 

 showed that there was an enormous difference in the tempera- 

 tures at which various fats and oils dissolved without turbidity 

 in acetic acid. By the work of Allen and Hurst it was shown 

 that the strength of acid made a considerable difference. Chatta- 

 way, Pearmain, and Moor have investigated the subject and 

 recommend the following procedure for butters : 2-75 grammes 

 of butter fat which has been previously dried (preferably by 

 mixing with dried pellets of filter paper and filtering through 

 a dried filter) are weighed into a test-tube provided with a stopper ; 

 3 c.c. accurately measured of acetic acid (containing 99-5 per 

 cent. C 2 H 4 2 ) are run into the tube, and this is placed in a beaker 

 of water. The water is heated gradually and the tube shaken 

 till the solution is clear ; the water is then allowed to cool gradu- 

 ally, and the temperature at which a turbidity appears in the 

 tube is measured by a thermometer held in close proximity. 

 By slightly warming up and cooling down again, a second deter- 

 mination can be obtained. 



Undue heating of the sample should be avoided, both in the 

 preparation of the fat for analysis and during the performance of 

 the test. 



