Cysteine test for sulphur: Significance: Cysteine test for sulphur is used for the detection of sulphur containing amino acids. Reagents: Sodium hydroxide (NaOH) Lead Acetate Principle: Protein or amino acids when heated with sodium hydroxide, sulphur splits out as sodium sulphide, which on reaction with lead acetate, forms grayish brown to black precipitate of … [Read more...]