A mixture of
100 g. of phthalide (Note
1) and
100 g. of powdered potassium cyanide is placed in a
2-l. round-bottomed flask fitted with a stirrer and a thermometer. The stirred mixture is heated to 180–190° (internal temperature) for 4–5 hours in an
oil bath (Note
2). One liter of water is added to the cooled mass, and the mixture is stirred until the solid salts are dissolved (Note
3). Any insoluble material that separates is removed by filtration (Note
4). Under a
hood,
6 N hydrochloric acid (20–60 ml.) is added to the dark aqueous solution until it becomes turbid (Note
5). The solution is carefully neutralized with
sodium bicarbonate (Note
6), a few grams of
Norit is added, and the mixture is stirred for several minutes and filtered. The nearly colorless filtrate is acidified with
40–50 ml. of concentrated hydrochloric acid and, after cooling in an
ice bath, is filtered with suction. The yield is
80–100 g. (
67–83%) of white crystals which melt at
113–115° (Note
7).