Note on the sodium nitro‐prusside reaction for acetone

LEGAL first showed that Weyl's reaction for creatinin was also given by acetone. The reaction consists in the addition of a few drops of a 5 0/0 solution of sodium nitro-prusside, followed by 1 0/0 sodium hydrate. A red colour is produced both with acetone and creatinin solutions. Le Nobel' elaborated the test by showing in the case of acetone that acidifyinog with acetic acid changed the red to magenta, and that acetone solutions even when too dilute to produce a red with alkali and nitro-prusside yield a red purple colour when acidified with acetic acid. He also describes the reaction with ammonia and mentions that adding mineral acid in instufficient amount to neutralize the ammonia improves the delicacy of the test. B itto2 applied the reaction to a vast number of aldehydes and ketones. He preferred the use of potassium hydrate as alkali, and he describes the colour changes on subsequent acidification with phosphoric acid. His general conclusion is, that bodies with the group-CHa-CO give the reaction. In testing for acetone in urine, the presence of creatinin prevents the direct application of the sodium nitro-prusside test when a fixed alkali is used. If however ammonia be used as alkali the creatinin does not react, at all events not in the concentrations normally present in the urine. But in testing the delicacy of the ammonia nitro-prusside reaction it, was found that it was limited by an acetone concentration of 1 in 600. The following description indicates how a strikingly delicate and characteristic acetone reaction may be obtained. The solution of acetone or urine containing the same is taken in a quantity of 5-10 c.c. A solid ammonium salt is added, then 2-3