A 2-l. round-bottomed flask is fitted with a rubber stopper carrying a Soxhlet extractor (Note 1) which in turn is fitted with an efficient reflux condenser. In the flask are placed 1190 g. (1500 cc., 20.5 moles) of commercial acetone (Note 2) and a few pieces of porous plate to produce even boiling. Two of the usual paper thimbles are placed in the extractor, one above the other. The lower one is filled nearly full of barium hydroxide; the top one is filled about three-quarters full of the same substance (Note 3), and the remainder of the space is filled with glass wool.

The flask is heated on a steam bath or in an oil bath. The heat is so regulated that the acetone refluxes back into the extractor rather rapidly. As the reaction proceeds the boiling point of the mixture rises and more steam has to be turned on or the temperature of the oil bath has to be raised. The flask should finally be lowered as far as possible into the cone of the steam bath. The reaction is complete when the liquid no longer boils when heated as hot as possible on the steam bath. This usually requires ninety-five to one hundred and twenty hours (Note 4). The refluxing may be interrupted at any time for as long as desired. The liquid in the flask has now a specific gravity of about 0.91 (20°) which corresponds to about 80 per cent of diacetone alcohol (Note 5). The only loss of material is by volatilization of the acetone through the top of the condenser; this generally amounts to several per cent.

The crude diacetone alcohol is purified by distillation. The 2-l. round-bottomed flask is fitted with a three-bulbed Glinsky fractionating column and a well-cooled condenser. The flask is heated in an oil bath, the temperature of which is gradually raised to 125°. The temperature of the bath is held at this point until no more acetone distils over, the temperature at the top of the column registering about 70° when the process is complete. The recovered acetone, containing a few per cent of diacetone alcohol, amounts to about 200 g. and can be used to prepare more material. The residual liquid has a specific gravity of 0.928 (20°) and contains about 95 per cent of diacetone alcohol. It is transferred to a 2-l. Claisen flask and distilled under reduced pressure (Note 6). A little acetone first comes over and then the diacetone alcohol distils smoothly at 71–74°/23 mm. The yield is 850 g. (71 per cent of the theoretical amount based on the total acetone employed). The entire distillation requires about four hours.