MTDATA – Phase Diagram Software from the National Physical Laboratory

 

 

 

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RANGE

Function:

The command RANGE is used to define the Type 3 components of which the potentials vary respectively along the abscissa and ordinate and assigns the range of values by fixing the maximum and minimum values for each of the axes. A Type 3 component may be any substance chosen from the substance list that is orthogonal to all other components. See general comments of SET. 

Parameters:

lgt_pressure(*)

lgt(activity)

lgt_molality(*)

Eh

pH

Defaults:

Undefined

Examples:

range lgt_pressure(12) -12 2 l_p(4) -30 0 !

range pH 0 14 !

range lgt_activity(C<graphite>) -5 0 !

range l_p(S2<gas>) undefined !

range l_p(O2<gas>) -25 0 l_p(SO2<gas>) -30 0 !

LGT_MOLALITY(*), LGT_PRESSURE(*), LGT_ACTIVITY(*), Eh, pH take the values <minimum value, maximum value>/ UNDEFINED

LGT_MOLALITY(*)

used to range the molality of a substance in aqueous solution, where * is any valid substance formula with a phase label or a substance number from the substance list. See general comments.

LGT_PRESSURE(*)

used to range the partial pressure of a gaseous species, where * is any valid substance formula with a phase label or a substance number from the substance list. See general comments.

LGT_ACTIVITY(*)

used  to range the notional activity, mainly of condensed substances, specified by *, where * is a valid substance number or a valid substance formula and phase label, as dispalyed in LIST SYSTEM SUBSTANCES.

Eh

used to range Eh. The units are in volts

pH

used to range pH in aqueous systems.

General comments:

Substances that are assigned a RANGE become Type 3 components. The first is assigned to the abscissa and the second to the ordinate. In order to assign new values to the RANGEs of the current Type 3 components, it is sufficient to enter the new range in exactly the same way as originally. However, in  order to change the Type 3 components, it is essential to undefine one of the existing components, as in the  examples, and then to RANGE both the new Type 3 components, even if one of them is unchanged. The range should not go beyond the permitted maximum for the property unless the options in COMPUTE are relaxed. The permitted maxima are partial pressure, 100; molality, 1; activity, 1. 

 

Updated 7 July 2010