112 MASS. EXPERIMENT STATION BULLETIN 166. 



yield hydrocarbons of the ethane and possibly other series. In vacuo 

 they can be distilled with or without superheated steam. 



Most of the natural fats and oils contain but a small amount of volatile 

 (soluble) fatty acids, generally below 2 Reichert-Meissl number. Some 

 prominent exceptions have already been enumerated, being characterized 

 by saponification numbers exceeding 210. See supplementary notes under 

 "Saponification Number." The high Reichert-Meissl numbers of dolphin 

 and porpoise oils may be due to valeric acid. The amount of volatile or 

 soluble acids in those oils and fats whose saponification number does not 

 exceed 195 is inappreciable. 



Among the oils and fats with a high volatile acid content might be men- 

 tioned ^ myrtle seed oil, croton oil, oleander oil, senega root oU, lycopo- 

 dium oil, apeiba oU, dolphin oU, macassar oil, muriti fat, mocaya oil, palm 

 kernel oil, coconut oU and tonka butter, having Reichert-Meissl numbers 

 between 5 and 15; and spindle tree oil, malukang oil, dolphin jaw oil, por- 

 poise body oil, porpoise jaw oil, brown fish oil and butter fat, having 

 Reichert-Meissl numbers ranging from 25 to 50, or even greater in some 

 instances. 



The amount of volatile acids is likely to increase with the age of the 

 sample. 



The results of Wechsler ^ and other investigators indicate that volatile 

 acids of higher molecular weight distill over before the lower acids, espe- 

 cially in cases where the neutrality of the solution is destroyed gradually 

 by several additions of acid instead of one, thus fractionating the dis- 

 tillates. 



Neutralization Number and Mean Molecular Weight. — The titrated 

 volatile acids' resulting from the determination of the Reichert-Meissl 

 number are evaporated in a tared platinum dish and dried to constant 

 weight in an oven at 100° C. From the weight (w) of the salts and the 

 quantity (v) of N/10 alkali used, the mean molecular weight (m) and the 

 neutralization number (n) can be calculated by the formulas — 



RCOONa-Na+H= RCOOH 



^ ^ 40.008 (w -.0021992 v) 

 .0040008 V 

 ^ 10000 (w -.0021992 v) 



V 



_ 56108 

 m 



Blank determinations should be run with every new lot of reagents, 

 both by distillation (Reichert-Meissl number) and by evaporation of the 

 titrated portion (salts), and deducted in the calculation. 



Limit of error, 1 unit molecular weight. 



' Lewkowitsch, Analysis of Oils, Fats and Waxes, 1, p. 423 (1913). 



2 Jour. Soc. Chem. Indus., 1894, p. 179. (From Lewkowitsch.) 



' Using N/10 sodium hydroxide, prepared irojn caustic alkali that is free from carbonate and 

 other impurities. The solution should be filtered frequently to remove silica arising from de- 

 composition of the glass. 



