this potassium oxalate monohydrate dissolved in 5 ml of water the resulting mixture was stirred for 2 hours at 60 u00b0 c the resulting mixture was concentrated to 5 ml and then cooled to 0 u00b0 c the resulting white crystals were collected by filtration washed with a small amount of water of 0 u00b0 c and then with ethanol and dried under vacuum to obtain a compound no 5 elementary analysis calculated c 21 82 h 3 66 n 7 27 pt 50 63 found c 22 01 h 3 71 n 6 98 pt 52 0 in example 4 the solution of 636 mg of sodium chloride dissolved in 5 ml of water was replaced by a solution obtained by dissolving 378 mg of malonic acid in 6 90 ml of 1n aqueous sodium hydroxide solution the mixture resulting from addition of this solution was stirred for 8 hours at 50 u00b0 c the reaction mixture was concentrated to 5 ml and then cooled to 0 u00b0 c the resulting white crystals were collected by filtration washed with a small amount of water of 0 u00b0 c and then with ethanol and dried under vacuum to obtain a compound no 6 elementary analysis calculated c 24 06 h 4 04 n 7 02 pt 48 85 found c 24 38 h 4 27 n 6 80 pt 48 4 in example 4 the solution of.