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Keywords

SOLUTION_MASTER_SPECIES

This keyword is used to define the correspondence between element names and aqueous primary and secondary master species. The alkalinity contribution of the master species, the gram formula weight used to convert mass units, and the element gram formula weight also are defined in this data block. Normally, this data block is included in the database file and only additions and modifications are included in the input file.

Example 

Line 0:  SOLUTION_MASTER_SPECIES 
Line 1a:     H            H+      -1.0   1.008          1.008
Line 1b:     H(0)         H2      0.0    1.008
Line 1c:     S            SO4-2   0.0    SO4            32.06
Line 1d:     S(6)         SO4-2   0.0    SO4
Line 1e:     S(-2)        HS-     1.0    S
Line 1f:     Alkalinity   CO3-2   1.0    Ca0.5(CO3)0.5  50.04

Explanation

Line 0: SOLUTION_MASTER_SPECIES

Keyword for the data block. No other data are input on the keyword line.

Line 1: element name, master species, alkalinity, (gram formula weight or formula), gram formula weight of element

element name--name of an element or an element name followed by a valence state in parentheses. The element name must begin with a capital letter, followed by zero or more lower case letters or underscores ("_").

master species--formula for the master species, including its charge. If the element name does not contain a valence state in parentheses, the master species is a primary master species. If the element name does contain a valence state in parentheses, the master species is a secondary master species. The master species must be one of the species defined in the SOLUTION_SPECIES data block.

alkalinity--alkalinity contribution of the master species. The alkalinity contribution of other aqueous species will be calculated from the alkalinities assigned to the master species.

gram formula weight--default value used to convert input data in mass units to mole units for the element or element valence. Either gram formula weight or formula is required, but items are mutually exclusive. For alkalinity, it is the gram equivalent weight.

formula--chemical formula used to calculate gram formula weight used to convert input data from mass units to mole units for the element or element valence. Either gram formula weight or formula is required, but items are mutually exclusive. For alkalinity, it is the formula for the gram equivalent weight.

gram formula weight for element--required for primary master species and must be the gram formula weight for the pure element, not for an aqueous species.

Notes

Line 1 must be repeated for each element and each element valence state to be used by the program. Each element must have a primary master species. If secondary master species are defined for an element, then the primary master species additionally must be defined as a secondary master species for one of the valence states. PHREEQC will reduce all reaction equations to a form that contains only primary and secondary master species. Each primary master species must be defined by SOLUTION_SPECIES input to have an identity reaction with log K of 0.0. The treatment of alkalinity is a special case and "Alkalinity" is defined as an additional element. In most cases, the definitions in SOLUTION_MASTER_SPECIES for alkalinity and carbon in the default database files should be used without modification.

The gram formula weight and formula are defined for convenience in converting units. For example, if your data for nitrate are consistently reported in mg/L of nitrate as NO3-, then gram formula weight should be set to 62.0 or formula should be set to "NO3". Then it will not be necessary to use the as or gfw options in the SOLUTION keyword data block. If nitrate is reported as mg/L as N, then gram formula weight should be set to 14.0 or formula should be set to "N". These variables (gram formula weight and formula) are only used if the concentration units are in terms of mass; if the data are reported in moles, then the value of the variables is unimportant. The value of gram formula weight for element is required for primary master species and its value is used to calculate the gram formula weight when a formula is given, either in SOLUTION_MASTER_SPECIES or SOLUTION keyword data block.

Example problems

The keyword SOLUTION_MASTER_SPECIES is used in example problem 1. See also the listing of the default database file in Attachment B.

Related keywords

SOLUTION and SOLUTION_SPECIES.

Example
Explanation
Notes
Example problems
Related keywords
User's Guide to PHREEQC - 07 MAY 96
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