KIRSCHNER PROCESS. 323 



Kirschner's Modification. — To the 100 c.c. of the distillate 

 of volatile fatty acids obtained in the Polenske process, which 

 has been neutralised, 0-5 f.'iamme of finely powdered silver sulphate 

 is added, and after standing for an hour with occasional shaking, 

 the liquid is filtered. 100 c.c. of the filtrate is placed in the dis- 

 tilling flask, 35 c.c. of water, which has been well boiled, and 

 10 c.c. of the sulphuric acid solution previously used added; a 

 long piece of aluminium wire is placed in the flask, and 110 c.c. 

 distilled as in the Polenske method ; of the distillate 100 c.c. are 



N 

 titrated with :j-^ alkali, and after correction for the tiiiim- obtained 



in a blank e.xpciiment, the Kirschner figure is calculated by 



\ 1 QO 4- "c 



multiplying the number of c.c. of ,V alkali bv ] -21 and bv — , , - 



(where j: -— the number of c.c. of alkiili added t(i the tiv.st distillate 

 for neutralisation). 



The presence of cocu-nut oil may be inferred if the I'olenske 

 figure is mew than 1-0 c.c. higher than tlmsi' uiven in tlic table 

 below. 



Kii'NchiUT tiL'un'. I\tlrii'-ki' li'^iu'C. 



2(i, . 3-2 



24, 2(i 



22. . .21 



20. I 11 



The Kirschner method is of es|)e(iiil value in estimating the 

 quantity of butter in mixtures containing small amounts when 

 large quantities of other fats are present — e.g., in margarine, 

 which under the Margarine Act is nt)t pei mitted to contain more 

 than 10 per cent, of btitter. 



The peiceiitiiue of butter may be calculated from the formula 



K — (0 2(12 p"«) + iiO'i) 

 ^ "" (1242 



where B = percentage of butter fat, 

 K = Kii'schner figure, 

 P = Polenske figure. 



The following table will uive the values of (0-262 P""^ + 

 0-09) :— 



