Why do we saturate ammonium sulphate in rothera's test?

Rothera's test is used to detect the presence of ketone bodies in a solution (eg urine). it utilizes sodium nitroprusside, liquid ammonia and ammonium sulphate. ammonium sulphate is used to concentrate the ketone bodies to the center of the solution. the other 2 constituents react with ketone bodies to form pink coloured polymerized compound. Rothera's test is used to detect the presence of ketone bodies in a solution (eg urine). it utilizes sodium nitroprusside, liquid ammonia and ammonium sulphate. ammonium sulphate is used to concentrate the ketone bodies to the center of the solution. the other 2 constituents react with ketone bodies to form pink coloured polymerized compound. Ammonium ion is used to precipitate the proteins that may be present.. Because proteins can give a positive result to Rothera's test as well..