Filter with the aid of suction, dissolve the crystals in 20 ml of boiling water containing 1 g of sodium bicarbonate, filter while hot, cool the filtrate, filter with suction, wash with 5 ml of methanol-water mixture (1 in 2) and dry in air.
Filtreeritakse vaakumi abil, kristallid lahustatakse 20 ml keevas vees, mis sisaldab 1 g naatriumvesinikkarbonaati, filtreeritakse kuumalt, filtraat jahutatakse, filtreeritakse vaakumi abil, pestakse 5 ml metanooli ja vee seguga (1 : 2) ning kuivatatakse õhu käes.