### Model II: Inputs for Batch Calculations

Data for one or more cases are entered or pasted into the text box. One problem is entered per line, with a limit of 100 problems. Note that data for each problem can be allowed to "wrap" onto two or more lines if necessary. However, carriage returns ("Enter" on the keyboard) should only occur at the end of the input data for each problem because the system uses them to divide the input into separate problems.

Each line of input must contain the following: temperature (K), system pressure (set this to 1.0 atm), system volume (set this to 1.0 m3), the case type (1, 2 or 3), the water dissociation option, the fixed RH or total moles of water (depending on the value of case type), the number of moles of each ion, and then a series of integers giving options related to trace gas equilibration and the solid phases. Amounts of organic species (if any), and their gas and solids options, follow.

Input for one example problem, which includes two organic compounds in addition to inorganic ions, is given below. Note that the line below has been split horizontally after item u, for ease of viewing. However, the input for each individual problem should be pasted into the text box as a single line. The letters beneath each number are for explanatory purposes (see below) and are not part of the input data.

```298.15 1.00 1.00  1  0  0.420  3.0 0.0 0.0   1.0 1.0 0.0 0.0 0.0 0.0   3 3 3 3 3   0
a     b    c    d  e   f      g   h   i     j   k   l   m   n   o    p q r s t   u

1.5 1.0   0 0   4 0   0 0
A       B     C     D
```

The meaning of each value is now described:

a – temperature (K). Valid range is 180 K to 330 K.

b – system pressure (here 1 atm). It is recommended at present that this value is left unchanged.

c – system volume (here 1 m3). It is recommended at present that this value is left unchanged.

d, f – water case (d, integer) and associated value (f, real). d = 1 means that the relative humidity of the system is to be fixed to the value of f, which in this example is 42% (specified as a fraction). The allowable range is 10% to 99% (i.e., 0.1 to 0.99).

The alternative water cases are, first, d = 2 for which f must be the total number of moles of water in the system. Here the program will solve for the equilibrium distribution of water, and so will give the calculated RH as an output. Second, d = 3, for which f is again the total number of moles of water in the system, but in this case it is not allowed to partition into the vapour and remains in the condensed phase as a liquid, ice, or water of hydration.

e – this is the water dissociation option. A value of -1 means that dissociation is not calculated for any input conditions. A value of zero means that if both numbers of moles of H+ and OH are zero on input, then H2O dissociation will remain off, and neither ion will be a variable in the calculations. If either H+ or OH is present on input, then the other will be made a variable and water dissociation will be on. A value of 1 means that water dissociation will always be calculated, and both H+(aq) and OH(aq) will be made variables in the calculation, even if their input amounts are zero.

g-o – these values are, in order, the numbers of moles of H+, NH4+, Na+, SO42−, NO3, Cl, Br, OH and NH3 present. For Model II the values for Na+, Cl and Br must be set to zero.

p – this controls how gas phase HNO3 is treated by the program. A value of "0" means that HNO3(g) can be formed and will be partitioned between the condensed and gas phases if the ions NO3, and associated H+, are present in the system. A value of "3" means that HNO3(g) is assumed not to occur, hence all NO3 (and associated H+) remain in the condensed phase. A value of "4" means, again, assume no formation of HNO3(g) but report its equilibrium partial pressure over the liquid phase (if it exists, and also contains both H+ and NO3). No other values of p are permitted.

q – as p above, for the gas HCl (q must be set to "3" for Model II).

r – as p above, for the gas NH3.

s – as p above, for the gas H2SO4.

t – as p above, for gas HBr (t must be set to "3" for Model II).

u – the number of solids whose options are to be individually entered. In the above example, u is 0, which means that the program will look for all the possible solids that can form, and include them in the equilibration. If u is equal to 1 or more, then it must be followed by the reference numbers (see Table 1 further below) and associated option values of the u solids to be treated specially. For example, "1 6 3" instead of "0" would mean:

• 1 solid phase option will be specified
• reference number = 6 (i.e., H2SO4 · 4H2O)
• option = 3 (means exclude from calculation).

The effect of this instruction is therefore to switch off H2SO4 · 4H2O formation in the calculation, and would be used to investigate the behaviour of supersaturated solutions. (The only other available option is "4", which means exclude from the calculation but report the saturation ratio.) Reference numbers of all the solids treated by Model II are given in Table 1 at the end of this page.

As a further example, if we wished to switch off both H2SO4 · 4H2O and HNO3 · 3H2O formation in a calculation, then we would enter:

2   6 3   9 3  (9 being the reference number of HNO3 · 3H2O).

Note that, if we are equilibrating to a fixed RH below 273.15 K then ice formation should always be switched off (1  1 3, or 1  1 4), because if it forms, then that would also define the water partial pressure in the system resulting in a probable thermodynamic inconsistency.

If no organic species have been selected for the system, no further entries on the data line are required and the instructions below can be ignored.

Organic compounds

Following the options for the inorganic solids (u, above) the amounts and options of all organic species selected for the system should be entered, in the order in which they are listed on the Batch Calculations page. In the example input line on this page we assume two organic compounds, but there can be any number. (If there are no organic compounds, then the data input line ends with item u and the rest of these instructions can be ignored.)

A – the numbers of moles of the organic compound, in the same order as they appear on the Batch Calculations page.

B – enter the gas options for each of the organic species, again in the same order the species are listed on the Batch Calculations page. The integer codes that are used are the same as those for the inorganic gases. Possible values are: 0 - allow partitioning into the gas phase if a vapour pressure or Henry's law constant has been specified; 4 - restrict the species to the condensed phases (solids and/or liquids) and report the equilibrium partial pressure; 3 - restrict the species to the condensed phases (solids and/or liquids) but do not report the equilibrium partial pressure. If any organic species does not form a gas, because no vapour pressure or Henry's law constant has been specified on the properties page, enter a zero '0'.

C – enter the solid option for each organic species in the system. The integer codes (0, 3 or 4) are the same as those for the inorganic solids (see item u). If the organic species cannot form a solid, because no activity product has been specified on the properties page for the compound, then enter a zero '0'.

D – these are the organic amine salt options. The model is able to calculate the formation of aminium sulphate, nitrate, and/or chloride salts in systems containing amines (that have been neutralised to aminium ions by H+) and the three inorganic anions. The options for all three salts are represented, for each amine, by a single integer as follows. The option value is the sum of the following codes:

• 1 - switch off formation of aminium sulphate salt
• 2 - switch off formation of aminium nitrate salt
• 4 - switch off formation of aminium chloride salt

So, if the formation of all three salts is to be switched off then the integer option value is 1 + 2 + 4 = 7. If only the sulphate and chloride salts are to be switched off then the option value will be 1 + 4 = 5. If only the chloride salt is to be switched off then the value of the option is 4. If all salts are to be allowed to form (i.e., not switched off) then the option value is zero '0'. A value of zero should also be entered for each organic that is not an amine, and for which this option is therefore irrelevant. Note also that the Cl ion is not present in Model II, and therefore the code '4' does not apply here.

#### Table 1: Reference Numbers of Solids for Model II

No.   Solid          No.   Solid
1 ice        11 (NH4)3H(SO4)2
3 H2SO4 · H2O        12 NH4HSO4
4 H2SO4 · 2H2O        13 NH4NO3
5 H2SO4 · 3H2O        14 2NH4NO3 · (NH4)2SO4
6 H2SO4 · 4H2O        15 3NH4NO3 · (NH4)2SO4
7 H2SO4 · 6.5H2O        16 NH4NO3 · NH4HSO4
8 HNO3 · H2O        28 HCl · 3H2O
9 HNO3 · 3H2O        29 HNO3 · 2H2O
10 (NH4)2SO4