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Các thuật ngữ trong ISO (2)

pH value

decadal logarithm of the hydrogen ion activity multiplied with (−1)

$mml_m1$

where

	$mml_m2$	is the activity of the hydrogen ion, in mol/kg;
	m⁰	is the standard molality (1 mol/kg);
	$mml_m3$	is the activity coefficient of the hydrogen ion;
	$mml_m4$	is the molality of the hydrogen ion, in mol/kg.

Note 1 to entry: Molality is understood as moles per kilogram solvent.

Note 2 to entry: The pH value is not measurable as a measure of a single ion activity. Therefore, pH(PR) values of solutions of primary reference material are determined, which are approximate to it and can be attributed to it. This is based on a worldwide agreement, see ISO 80000-9:2009, Annex C.

[SOURCE: ISO 23496:2019, 3.2]

ISO 23497:2019(en), 3.2

measure for the acidic or basic character of an aqueous solution

Note 1 to entry: Notation of pH: the "p" and the "H" are upright on one line.

Note 2 to entry: The acidic character is determined by the activity of the existing “hydrogen ions”.

[SOURCE: ISO 23496:2019, 3.1]

ISO 23497:2019(en), 3.1

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