27 CFR 21.119: Nicotine solution.

(a) Composition. Five gallons of an aqueous solution containing 40 percent nicotine; 3.6 avoirdupois ounces of methylene blue, U.S.P.; water sufficient to make 100 gallons.

(b) Color. One mL of the nicotine solution (previously agitated in the presence of air) is measured into 100 mL of water and thoroughly mixed. Fifty mL of this colored solution is compared, using Nessler tubes, with 50 mL of a standard color solution containing 5 grams of CuSO4·5H2 O, C.P. in 100 mL of water. The color intensity of the solution tested should be equal to or greater than that of the standard solution.

(c) Nicotine content. The above solution must contain not less than 1.88 percent of nicotine determined by the following process: 20 mL of the solution are measured into a 500 mL Kjeldahl flask provided with a suitable bulb tube, 50 mL of 0.1 N NaOH added and the mixture distilled in a current of steam until the distillate is no longer alkaline (about 500 mL). The distillate is then titrated with 0.1 N H2SO4 using rosolic acid or methyl red as indicator. Not less than 23.2 mL should be required for neutralization.