In a
5-l. flask are placed
100 g. (0.44 mole) of nitrobarbituric acid (p. 440) and
600 cc. of concentrated hydrochloric acid, and the mixture is heated on a boiling
water bath. To the hot mixture are added
250 g. (2.1 gram atoms) of mossy tin and
400 cc. of hydrochloric acid over a period of about thirty minutes; heating is continued until there is no yellow color in the liquid (Note
1). The solution is treated with about
3 l. more of concentrated hydrochloric acid and heated until all the white solid is in solution.
Norite is added, and the hot mixture is filtered through a
sintered-glass funnel (Note
2). The filtrate is allowed to stand in an
icebox overnight, and then the precipitate (Note
3) of
uramil is collected on a filter and washed with liberal quantities of
dilute hydrochloric acid and finally with water (Note
4). The filtrate is concentrated under reduced pressure to about 1 l. and cooled overnight. The additional
uramil thus obtained is collected on a
Büchner funnel and added to the first product (Note
5). The
uramil is dried in a
desiccator over concentrated
sulfuric acid, and finally over
40 per cent sodium hydroxide to remove
hydrochloric acid (Note
6).
Uramil is a fine, white powder which becomes pink to red on standing. The yield of a product which does not melt below
400° is
40–46 g. (
63–73 per cent of the theoretical amount).