large quantities are present, a dark brown precipitate is formed. It was
soon found, however, that other substances than amyl alcohol produce
brown colored solutions with silver nitrate; and Bouvier[1] observed
that on adding potassium iodide to alcohol containing fusel oil, the
solution is colored yellow, from the decomposition of the iodide.
Subsequently Böttger[2] proved that potassium iodide is not decomposed
by pure amyl alcohol, and that the decomposition is due to the presence
of acids contained in fusel oil. More accurate results are obtained by
using a very dilute solution of potassium permanganate, which is
decomposed by amyl alcohol much more rapidly than by ethyl alcohol.

[Footnote 1: Zeitschrift f. Anal. Chem. xi., 343.]

[Footnote 2: Dingler's Polytech. Jour., ccxii., 516.]

Depré[3] determines fusel oil by oxidizing a definite quantity of the
alcohol in a closed vessel with potassium bichromate and sulphuric acid.
after removal of excess of the oxidizing reagents, the organic acids are
distilled, and, by repeated fractional distillation, the acetic acid is
separated as completely as possible. The remaining acids are saturated
with barium hydroxide, and the salts analyzed; a difference between the
percentage of barium found and that of barium in barium acetate proves
the presence of fusel oil, and the amount of difference gives some idea
of its quantity. Betelli[4] dilutes 5 c.c. of the alcohol to be tested
with 6 to 7 volumes of water, and adds 15 to 20 drops of chloroform and
shakes thoroughly. If fusel oil is present, its odor may be detected by
evaporating the chloroform; or, by treatment with sulphuric acid and
sodium acetate, the ether is obtained, which can be readily recognized.
Jorissen[5] tests for fusel oil by adding 10 drops of colorless aniline
and 2 to 3 drops of hydrochloric acid to 10 c.c. of the alcohol. In the