15-425 Izikulufu zokugcina izitsha zifanele ukupakishwa kwezinhlobonhlobo zemithi ephakathi, amakhemikhali anenani eliphakeme, ama-reagents amakhemikhali, ama-reagents ebhayoloji, izimonyo, ama-essensi namafutha, njll. Ifanele isitoreji sesikhathi eside nokuthuthwa kwemikhiqizo, futhi isebenza kahle kakhulu yokuvala.