A standard solution is made up containing 1 gram of colourless furfural in 100 c.c. of pure spirit of 50 per cent. strength, and from this, other standard solutions are prepared containing 01, 0 01, and 0 001 gram respectively of furfural per 100 c.c. of similar spirit.

Ten c.c. of the distillate to be examined are placed in a small Nessler tube (25 c.c. capacity), and similar tubes are prepared containing from 05 c.c. upwards of the standard 0001 per cent. furfural solution, the volume in each case being made up to 10 c.c. with pure 50 per cent. alcohol.

To each tube is added 0 5 c.c. of freshly prepared aniline acetate (made by mixing equal volumes of pure redistilled aniline, glacial acetic acid, and water), and the contents well mixed. When furfural is present a fine pink colour is soon developed, and at the end of fifteen minutes the sample is compared with the standards; the quantity of furfural present is thus ascertained.