en>John of Reading: Typo/general fixing, replaced: litterature → literature using AWB

2013-06-17T19:25:44Z

Typo/general fixing, replaced: litterature → literature using AWB

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{{Infobox software
| name = aqion
| released = {{start date|2012|01|01}}
| latest release version = version 4.3.3
| latest release date = Feb 2014
| programming language = [[C++|C/C++]]
| operating system = [[Windows]]
| size = 1.5 MB
| language = English, German
| website = [http://www.aqion.de aqion.de]
}}

'''Aqion''' is a hydrochemistry software tool. It bridges the gap between scientific software (such like '''PhreeqC'''<ref name="Parkhurst">Parkhurst, D.L. and C.A.J. Appelo: User's Guide to PHREEQC (version 2), a computer program for speciation, batch-reaction, one-dimensional transport and inverse geochemical calculations. [[USGS]] Water-Resources Investigations Report 99-4259, 1999</ref>)
and the calculation/handling of "simple" water-related tasks in daily routine practice. The software aqion is free for private users, education and companies.

==Motivation & History==
First. Most of the [[geochemical modeling#Software programs in common use|hydrochemical software]] is designed for experts and scientists. In order to flatten the steep learning curve aqion provides an introduction to fundamental water-related topics in form of a "chemical pocket calculator".

Second. The program mediates between two terminological concepts: The calculations are performed in the "scientific realm" of thermodynamics (activities, speciation, log K values, ionic strength, etc.). Then, the output is translated into the "language" of common use: molar and mass concentrations, alkalinity, buffer capacities, water hardness, conductivity and others.

History. Version 1.0 was released in January 2012 (after a half-year test run in 2011). The project is active with 1-2 updates per month.

==Features==
* Validates aqueous solutions (charge balance error, parameter adjustment)
* Calculates physico-chemical parameters: [[alkalinity]], buffer capacities ([[Acid neutralizing capacity|ANC]], BNC), [[water hardness]], [[ionic strength]]
* Calculates aqueous speciation and [[coordination complex|complexation]]
* Calculates [[pH]] of solutions after addition of chemicals ([[acid]]s, [[base (chemical)|bases]], [[salt]]s)
* Calculates the calcite-carbonate system (closed/open CO2 system, [[Langelier Saturation Index]])
* Calculates mineral [[Dissolution (chemistry)|dissolution]], [[Precipitation (chemistry)|precipitation]], and saturation indices
* Calculates mixing of 2 waters
* Calculates reduction-oxidation ([[redox]]) reactions
* Plots titration curves

==Fields of Application==
* Water analysis and [[water quality]]
* [[Geochemical modeling]] (in simplest form)
* Education

==Limits of Application==
* only [[inorganic chemistry|inorganic]] species (no organic chemistry)
* only [[equilibrium thermodynamics]] (no [[chemical kinetics]])
* only aqueous solutions with [[ionic strength]] ≤ 0.7 mol/L<ref>Note: The upper limit is sea water.</ref> (no [[brine]]s)

==Basic Algorithm & Numerical Solver==
There are two fundamental approaches in hydrochemistry: [[Law of Mass Action]] (LMA) and Gibbs Energy Minimization (GEM).<ref>http://www.kristall.uni-frankfurt.de/media/handouts/GEM-lecture.PDF</ref>
The programm aqion belongs to the category '''LMA approach'''. In a nutshell: A system of ''NB'' independent basis components ''j'' (i.e. primary species), that combines to form ''NS'' secondary species ''i'', is represented by a set of mass-action and mass-balance equations:

(1)       mass action law:        <math>\{i\} \,=\, K_i \, \prod_{j=1}^{N_B} \,\{j\}^{\nu_{i,j}} </math>        with i = 1 ... NS

(2)       mass balance law:        <math>[j]_{TOT} \,=\, [j] + \sum_{i=1}^{N_S}\, \nu_{i,j} \,[i] </math>        with j = 1 ... NB

where ''Ki'' is the [[equilibrium constant]] of formation of the secondary species ''i'', and νi,j represents the stoichiometric coefficient of basis species ''j'' in secondary species ''i'' (the values of νj,i can be positive or negative). Here, [[Activity (chemistry)|activities]] ''ai'' are symbolized by curly brackets {i} while [[concentration]]s ''ci'' by rectangular brackets [i]. Both quantities are related by the

(3)       activity correction:        <math>\{i\} \,=\, \gamma_{i} \, [i] </math>

with γi as the activity coefficient calculatesd by the [[Debye-Hückel equation]] and/or [[Davies equation]]. Inserting Eq.(1) into Eq.(2) yields a nonlinear polynomial function fj for the ''j-''th basis species:

(4)       <math>f_j (c_1,c_2,...,c_{N_B}) \,=\, [j]_{TOT} - [j] - \sum^{N_S}_{i=1} \frac{\nu_{i,j}}{\gamma_i}\, K_i\, \prod^{N_B}_{k=1} \{k\}^{\nu_{i,k}} \,=\,0 </math>

which is the ''objective function'' of the [[Newton-Raphson]] method.

To solve Eq.(4) aqion adopts the numerical solver from the open-source software ''PhreeqC''.<ref name="Parkhurst" /><ref>Remark: To keep things apart, the numerical solver of PhreeqC is outsourced from ''aqion.exe'' into a separate [[Dynamic-link library|DLL]].</ref>
The [[equilibrium constants]] ''Ki'' are taken from the thermodynamic database ''wateq4f''.
<ref>Ball J.W. and D.K. Nordstrom: WATEQ4F – User’s manual with revised thermodynamic data base and test cases for calculating speciation of major, trace and redox elements in natural waters, [[USGS]] Open-File Report 90-129, 185 p, 1991.</ref>

==Examples, Test & Verification==
The software aqion is shipped with a set of example solutions (input waters) and a tutorial how to attack typical water-related problems (online-manual with about 40 examples). More examples and exercises for testing and re-run can be found in classical textbooks of hydrochemistry.<ref>Stumm, W. and J.J. Morgan: Aquatic Chemistry, Chemical Equilibria and Rates in Natural Waters (3rd ed.), John Wiley & Sons, Inc., New York, 1996, ISBN 978-0471511854</ref><ref>Morel, F.M.M. and J.G. Hering: Principles and Applications of Aquatic Chemistry (2nd ed.), John Wiley, New York, 1993, ISBN 978-0471548966</ref><ref name="Appelo">Appelo, C.A.J. and D. Postma: Geochemistry, Groundwater, and Pollution. Taylor & Francis, 2005, ISBN 978-0415364287</ref>

The program was verified by benchmark tests of specific industry standards.<ref>[[DIN]] 38404-10: German standard methods for the examination of water, waste water and sludge - Physical and physicochemical parameters (group C) - Determination of calcite saturation of water (C 10)</ref>

==Screenshots==
<gallery>
File:Aqion input panel 3.5.gif|input panel for chemical elements
File:aqion pH calculator.jpg|output of pH calculator (example)
File:Aqion calcite carbonate system 3.5.gif|calculated parameters of the calcite carbonate system
File:Titration NaOH.gif|titration curves (example: addition of NaOH to a given input water)
</gallery>

==References==
{{Reflist}}

==External links==
* [http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/ PHREEQC]

[[Category:Chemistry software]]
[[Category:Computational chemistry software]]
[[Category:Science education software]]

Asymmetric simple exclusion process - Revision history

en>John of Reading: Typo/general fixing, replaced: litterature → literature using AWB