In a 2-gallon (8-l.) wide-mouthed bottle (Note 1) packed in ice-salt mixture are placed 630 g. (8.7 moles) of commercial (95 per cent) sodium nitrite and 5 kg. of chopped ice, and the mixture is well stirred. A cold (0–5°) solution of sodium bisulfite, made by saturating with sulfur dioxide a solution of 495 g. (4.7 moles) of anhydrous sodium carbonate in 1500 cc. of water, is now added slowly with hand stirring. When all is in, a sufficiently large quantity of the ice will have melted to allow a mechanical stirrer to be fitted. A stream of sulfur dioxide is now passed in, with continual stirring, the temperature being kept at 0–2°, until an acid reaction to Congo red paper is obtained and the dark color, which appears just before the reaction is complete, has faded. During the addition of the sulfur dioxide, 500 g. more of ice may be added.

The mixture is now transferred to a 12-l. flask, 495 g. (625 cc., 8.5 moles) of acetone is added, and the solution is heated on the steam bath to 70°. Heating is then discontinued, the flask wrapped in burlap in order to retard loss of heat, and the mixture allowed to stand overnight. The acid is then neutralized with a concentrated (50 per cent) solution of sodium hydroxide (about 720 g. of alkali is required), until a distinctly alkaline reaction to litmus is just obtained.

The resulting acetoxime is now distilled in a current of steam (Note 2), and the distillation is continued until a 5-cc. sample, shaken with 2 cc. of ether, yields no appreciable residue on evaporating the ether. To the distillate (2–2.5 l.) is added 600 cc. of concentrated hydrochloric acid, and the acid solution is distilled at atmospheric pressure until the distillate is free of acetone (Note 3). The residual liquor is then evaporated to dryness on the steam bath, either in an open dish or preferably under reduced pressure. The crude hydroxylamine hydrochloride so obtained, weighing 296–470 g. (49–77 per cent of the theoretical amount), is suitable for many purposes, but is best purified by recrystallization from half its weight of water. By systematic recrystallization of the product from several batches, the yield of pure product, which crystallizes in long flat needles, melting when dry at 150–154°, may be brought as high as 70 per cent of the theoretical amount (Note 4).

In order to prepare pure acetoxime (Note 5), the procedure is modified in the following way: After neutralizing the solution of acetoxime formed after the addition of acetone, the oily layer is separated and the aqueous solution shaken with two or three 150-cc. portions of benzene. The oil and benzene solutions are mixed, the water thereby thrown out is removed, and the oil fractionally distilled with the use of a column, the portion boiling 133–136° being collected as pure acetoxime. This product, which weighs 420–480 g. (67–76 per cent of the theoretical amount), solidifies in the receiver to colorless needles melting at 60–61°. The foreruns and aqueous liquors are best distilled with steam and the distillate converted into hydroxylamine hydrochloride as above, whereupon 75–90 g. of pure salt is obtained.