ISO 777:2005 specifies the procedure for the determination of acid-soluble calcium by atomic absorption spectrometry or by plasma emission spectrometry.
It is applicable to all kinds of paper, board and pulp.
It specifies a method to determine the acid-soluble part of the incineration residue, i.e. that part of the ignition residue obtained after incineration that is soluble in hydrochloric acid. If the residue is completely soluble, the result obtained by the procedure specified in ISO 777:2005 is taken as the total amount of calcium in the sample.