This section is from the book "Monograph on Flavoring Extracts With Essences, Syrups, and Colorings", by Joseph Harrop . Also available from Amazon: Monograph On Flavoring Extracts With Essences, Syrups And Colorings.
Oil of bitter almonds, adulterated with an admixture of nitro-benzole, may be detected by solution of potassa. The liquid is green if nitro-benzole is present, and upon dilution three layers are formed, the lower yellow, the upper green. Over night the green color changes to red.
*Proctor. *Zeitscher F. Anal. Chem., 1872, p. 316.
Oil of Bitter Almonds...........
2 fl. ounces.
Sulphate of Iron (U. S.).........
Lime (recently burnt)...........
Water, a sufficient quantity.
Dissolve the Sulphate of Iron in one-half (1/2) pint of Water; slake the Lime with one-half (1/2) pint of the same fluid, and mix them; shake this thoroughly with the Oil of Bitter Almonds in a bottle, then distill in a glass retort or small tin still, with a good refrigeratory, until the purified oil of bitter almonds has all distilled over, which is known by the distilled water ceasing to be milky and odorous. The heavy oil, after allowing time for its separation and subsidence, is removed for use.