Ninhydrin is often used to detect α− amino acids and also free amino and carboxylic acid groups on proteins and peptides. When about 0.5mL of a 0.1% solution of ninhydrin is boiled for one or two minutes with a few mL of dilute amino acid or protein solution, a blue color develops. Ninhydrin degrades amino acids into aldehydes, ammonia, and CO2 through a series of reactions to produce an intensely blue or purple pigment, sometimes called Ruhemann's purple.