70 DAIRY ANALYSIS 



flame, and replace the flask by a 25 c.c. cylinder ; 

 cool the flask for ten minutes in water at 10 C., 

 mix the distillate, and filter through a dry filter ; 

 use the first few c.c. to wash out a 100 c.c. flask, and 

 collect exactly 100 c.c. of the filtrate, and transfer 



this to a beaker, add a 

 little phenolphthalein and 



N 



titrate with baryta, 

 10 



strontia, or soda solution 

 till a pink colour appears ; 

 pour this back into the 

 flask, and again into the 

 beaker, and if the colour 

 is discharged continue the 

 titration. From the num- 

 ber of cubic centimetres 

 used, subtract the figure 

 obtained in a blank ex- 

 periment, and multiply the 

 result by i.i to obtain the 

 Reichert-Wollny figure. 



Wash out the condenser 

 with two successive quan- 

 tities of 9 c.c. each of cold 

 , water, collecting this in the 

 'cylinder and using it to 

 wash out the flask, and 

 pouring it through the 

 filter ; reject this filtrate, 

 and remove the funnel containing the filtrate to a clean 

 flask. Wash out the insoluble fatty acids from the con- 

 denser with three successive quantities of 10 c.c. each 

 of neutral alcohol, collecting each in the cylinder, and 

 pouring it through the filter ; titrate the combined 



filtrates with alkali after adding a little phenol- 

 phthalein ; the number of c.c. of -- alkali used gives 

 the Polenske figure. 





FIG. 3 5. Polenske Apparatus. 



