To a suspension of 800 g. of paraformaldehyde (corresponding to 26.7 moles of formaldehyde) (Note 1) in 5.5 l. of water containing 210 g. (4.77 moles) of acetaldehyde there is added 180 g. (3.22 moles) of powdered quicklime in small portions with vigorous mechanical stirring (Note 2). The rate of addition is so adjusted that the temperature rises to 50° in thirty minutes, and during the subsequent additions the temperature of the mixture is not allowed to exceed 55°. The mixture takes on a slightly yellow color. After the addition is complete, stirring is continued for three hours, the mixture is filtered by gravity, and the yellow filtrate is acidified with just enough dilute hydrochloric acid to give an acid reaction to litmus. Subsequent to the addition of 30 g. of Norite and stirring for five minutes, the solution is again filtered.

The filtrate, which should be colorless, is concentrated on the steam bath under reduced pressure (Fig. 23) (Note 3) until crystalline material begins to separate. The liquor, amounting to approximately 3 l., is heated on the steam bath at atmospheric pressure and filtered with suction while hot, any crystals remaining on the filter being washed through by aspiration of wet steam. The filtrate is allowed to stand in the refrigerator overnight and the first crop of crystals filtered off. This weighs approximately 300 g. and melts at about 237° (corr.). The mother liquor is concentrated to approximately 2 l. and a second crop obtained as above; this weighs 60–70 g. and melts at 242° (corr.). A third crop of 50–60 g. melting at 249° (corr.) is obtained by concentrating the mother liquor to 1.2 l. The mother liquor is finally concentrated to a sirup, when a fourth crop weighing about 10 g. and melting at 248° (corr.) is obtained.

The combined product, weighing 410-420 g., is recrystallized from an equal weight of hot water containing 10 cc. of concentrated hydrochloric acid. The color is removed by the addition of 5 g. of Norite. By suitably concentrating the mother liquors, second, third, and fourth crops may be obtained, all of which appear to be of the same purity as the first crop. The total yield is 360–370 g. (55-57 per cent of the theoretical amount) of a product melting at 258–260° (corr.) and containing negligible amounts of calcium (Note 4). The final residue, amounting to 20–30 g., leaves a considerable quantity of ash on ignition.