131 



The Reichert-Meissl value does not represent the total volatile or soluble 

 acids, but only a reasonably constant fraction, provided the operation is 

 conducted uniformally according to the prescribed method. 



From the Reichert-Meissl value the total volatile acids can be calcu- 

 lated, with considerable degree of accuracy. By the Reichert-Meissl process 

 of distillation from 85 to 89 per cent, of the total volatile acids are distilled. 

 (See Richmond's Dairy Chemistry, p. 264; Lewkowitsch, Fats, oils and waxes 

 Vol. 1, p. 332.) Then to calculate the total volatile or soluble acids* we make 

 use of the number of cubic centimeters of NaOH N/10 required to neutralize 

 the volatile acids obtained from five grams of fat. Then for the per cent, 

 of total volatile or soluble acids in the butter fat as recorded in Table I, cal- 

 culated as butyric acid, we have 30.00 X .0088 -^ 5 X 100/87 = 6.10 per cent, 

 of volatile acid as butyric acid, a result which agrees with the chemical an- 

 alysis of the butter fat Table I. For the soft portion of fat the total volatile 

 acids calculated from the Reichert-Meissl numbers gave 6.82 per cent., while 

 that obtained by direct determinations was 6.90 per cent., a difference of 

 .08 per cent. 



For the hard portion the total volatile acids calculated from the Reichert- 

 Meissl number gave 4.98 per cent., that found by direct determination 5.17, 

 a difference of .19 per cent. 



In the three analyses the total volatile acids calculated from the Reichert- 

 Meissl number is a close approximation to that found by direct determina- 

 tion, assuming that 87 per cent, of the volatile acids are distilled. 



The per cent, of volatile acids distilled vary with the rate of distillation, 

 size of distilling flasks, etc. But when the relation of the Reichert-Meissl 

 value and the total volatile acids are once determined, close approximations 

 can be made in the calculation of total volatile or soluble acids. 



The Reichert-Meissl value furnishes means to calculate the mean molecu- 

 lar weight of the volatile acids, and by the use of the mean molecular weight 

 the relative proportion of the different volatile acids entering into the gly- 

 cerides of butter are indicated. In Table I, in case of butter fat, we found 

 the Reichert-Meissl value to be 30.00, i. e., it reciuired 30 cubic centimeters 

 of N/10 potassium hydrate to neutralize the volatile acids obtained from 

 five grams of butter fat as determined by the Reichert-Meissl process. Since 

 the 30 cubic centimeters represent only 87 per cent, of the total volatile acid, 

 then for the total volatile acids present in five grams of fat it would reciuire 



34.48 cubic centimeters of N/10 potassium hydrate. Then to find the number 



j 



*For the purpose of calculating the total volatile acids, the factor 87 was used; this being in agree- 

 ment with Richmond and the work done at the Purdue Dairy Chemistry Laboratory. 



