198 



THE ANALYSIS OF MILK PRODUCTS. 



sum for ^ __ will give the ratio of propionic to total acid. Next 

 nine values of B (= ratio of butyric acid) are obtained from the 



equation B = -= Py , and a probable value of B is best 



o a o a 



obtained by summing the nine values 2 of , ~ a and P ? ~" a 



b a b a 



and taking 1 of the difference of the sums. The ratio of acetic 

 acid is 1 B P. A 10-inch slide rule is just good enough for 

 the calculation, or four-figure logarithms may be used. 



The examples worked out below will show the manner in which 

 the tables can be used to facilitate the working out of results. 

 The working is all put down, though, naturally, much would be 

 done mentally in practice. 



Mixture of 20 c.c. N acetic acid + 20 c.c. of N butyric acid 

 made up to 100 c.c. 



TABLE XXXVI. MIXTURE OF ACETIC AND BUTYRIC ACIDS. 



* From Table XXXIV. 



Mean value of 



f From Table XXXV. 

 = 0-499 



If calculated as a mixture of acetic, propionic, and butyric 

 acids, the value of (1) is O'OOl, (2) + O'OOl, (3) O'OOO, 



(4) O'OOO, (5) 0-002. It is evident that the value of 



y P a 



will be practically nothing (= - = O'OOl). The mean 

 value will be : " r06 



Butyric acid, 

 Propionic acid, . 

 Acetic acid, , 



0-500 



-0-001 



0-501 



