G01N31/00	Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroups; Apparatus specially adapted for such methods [4]
	Note(s) The observation of the progress of the reactions covered by groups G01N 31/02-G01N 31/22 by any of the methods specified in groups G01N 3/00-G01N 29/00, if this observation is of major importance, is classified in the relevant group covering the method.