Reilly and Hiciunbottom — Volatile Fatty Acids. 525 



Acetic Acid. Commercially pure glacial acetic acid was purified by 

 freezing out several times, and distillation over potassium permanganate, as 

 described by Bousefield and Lowry. 1 The distillate boiling at 116-117° C. 

 was fractionally distilled, a fraction boiling over a range of 02° C. being 

 reserved. Specimens from two different sources, (a) "glacial acetic acid pure 

 for analysis," and (b) " glacial acetic acid 50° ~E.,' i were also used. The constants 

 agreed within limits of experimental error. Table 5 gives acetic acid 

 distillation constants. 



Acetic Acid. 



Table 5. — (Concentration. 150 c.c. of solution requires 164-0 c.c. 0-1 N. 



Ba(OH) 2 to neutralize.) 



Propionic Acid. Samples of propionic acid from three different sources, 

 namely, "Kahlbaum's propionic acid," "propionic acid, extra pure," from British 

 Drug Houses, and a sample of pure propionic acid of unknown origin, were 

 fractionally distilled two or three times. The distillate collected between 

 140-2-140-5° C. (uncorr.) was used. The three samples gave results 

 agreeing closely among themselves. Table 6 gives the constants obtained. 



n-ButyricAcid. Kahlbaum's "brown label" "purest butyric acid" was 

 fractionated. For determination of the distillation constants, as given in 

 table, the acid collected over a range of 0"4° C. was used [boiling-point 

 163-163-4° C.]. The constants are tabulated in Table 7. 



'J. Chem. Soc, 1911, 99, 1432. 



