(1) Take 5mL of the aqueous solution (1 → 1000) of the product, add 1mL of potassium chromate solution (1 → 1000) and boil it to produce a peculiar odor ②.
(2) Take 5mL of this product's aqueous solution (1 → 1000), add 1mL of ninhydrin test solution, heat for 3min, and the solution will appear red purple to blue purple.
(3) Take 10mg of this product, add 0.5g of potassium nitrate and 2mL of sulfuric acid, heat it in water bath for 20min, add 5mL of hydroxylamine hydrochloride solution (1 → 10), place it in ice water for 10min to cool it, immediately add 8mL of 40% sodium hydroxide solution, place it, and it will appear red and purple ③.