Jump to content

User:Bsalonline/HSC Chemistry

From Wikipedia, the free encyclopedia
HSC Chemistry
Developer(s)Outotec Oyj [1][2]
Initial releaseInternal release: 1974; 50 years ago (1974), Public release: 1987; 37 years ago (1987)
Stable release
HSC Chemistry 8.0.3 / October 31, 2014; 9 years ago (2014-10-31)
Written in.NET Framework, C++
Operating systemMicrosoft Windows[3]: Windows Vista, Windows 7 or Windows 8
PlatformIA-32, x86-64
Available inEnglish
TypeScientific and Technical Computing [1]
LicenseProprietary commercial software
Websitewww.hsc-chemistry.com
Outotec Oyj
IndustryBasic resources, engineering
HeadquartersEspoo, Finland
ProductsMetal and mineral processing machinery and process engineering
Websitewww.outotec.com

HSC Chemistry is the thermochemical software with extensive databases and a flowsheet simulation module[1]. HSC Chemistry is designed for various kinds of chemical reactions and equilibrium calculations, as well as for process simulation which is linked with LCA (Life Cycle Assessment) analysis[1].

HSC Chemistry 8 is the latest version released on 31st October 2014 and it contains 24 calculation modules which are connected to the 12 databases as appropriate[1][4]. Most calculation modules operate like independent programs which may have data links with each other. All the calculation modules have their own user interface and manual. Most calculation modules utilize extensive thermochemical database with H (enthalpy),S (entropy) and Cp (heat capacity) data for more than 28000 chemical species[1][5]. This is also the reason for the name of the software. HSC Chemistry software makes conventional thermodynamic calculations fast and easy to carry out with personal computers[1]. Therefore HSC has a wide range of applications in scientific education, industry and research. Thermochemicalcalculations are useful, for example, when developing new chemical processes and improving old ones. HSC Chemistry is also a useful tool for universities and schools in chemical workshops and studies.

HSC Chemistry also contains modules for mineral processing and particle calculations, which are integrated with an extensive mineral database[1][5].

History

[edit]

HSC Chemistry is one of the first scientific software packages with versatile chemical, thermodynamic and mineral processing features. The first module was created to calculate equilibrium compositions in the Outokumpu Oyj sulfur plant gas line in 1974, by Timo Talonen. HSC digital database development started at the Helsinki University of Technology in 1979 by Dr. Antti Roine. The HSC Chemistry software development was started because there was no such software available. Originally HSC Chemistry was developed for Outokumpu Oyj as an internal tool to improve chemical process R&D efficiency. Later on in 1987 delivery to the other companies started[6]. The development of software and databases has been done in co-operation with several universities including: Helsinki University of Technology(Aalto University), Åbo Akademi University,Petrozavodsk State University, Luleå University of Technology, University of Kentucky, Montana Tech, Missouri University of Science and Technology, University of Turku, University of Jyväskylä, Tallinn University of Technology,Lappeenranta University of Technology ,University of Oulu , University of Eastern Finland, etc. Outokumpu Oyj founded a new company Outotec Oyj at 2006[2], this new company is based on Outokumpu Oyj technology business activities and IPR. The ownership of HSC Chemistry was also transferred to Outotec Oyj.

Version History

[edit]

Within the last 40 years, more and more calculation modules have been added to the package and databases have been expanded – and this work continues...

HSC Chemistry version history table[1]
# Versions Release Year License Featured Written in Platform Operating System
1. v0.1 1974 for internal use only First Equilibrium module Gibbs Fortran
2. v0.2 1979 for internal use only H,S, and Cp Database HP Unix
3. v0.3 1980 for internal use only Routine for activity coefficient calculations HP Unix
4. v0.4 1981 for internal use only Reaction Equation module HP Unix
5. v0.5 1983 for internal use only Heat Balance module HP Unix
6. v0.6 1986 for internal use only 2 modules, 1000 species QuickBASIC IBM DOS
7. v0.7 (I) 1987 for internal use only 2 modules, 2400 species QuickBASIC IBM DOS
8. v0.7 (II)* 1987 Public 2 modules, 2400 species QuickBASIC IBM DOS
9. v0.8 1989 Public 4 modules, 4600 species QuickBASIC IBM DOS
10. v1.0 1992 Public 5 modules, 5000 species Visual Basic,C++ Microsoft Windows
11. v1.1 1993 Public 5 modules, 5600 species Visual Basic,C++ Microsoft Windows
12. v2.0 1994 Public 7 modules, 7600 species Visual Basic,C++ Microsoft Windows
13. v3.0 1997 Public 7 modules, 11000 species Visual Basic,C++ Microsoft Windows
11. v4.0 1999 Public 13 modules, 15000 species Visual Basic,C++ Microsoft Windows
12. v5.0 2002 Public 15 modules, 17000 species Visual Basic,C++ Microsoft Windows
13. v6.0 2006 Public 19 modules, 20000 species, Sim module Visual Basic,C++ Microsoft Windows
14. v7.0 2009 Public 22 modules, 25000 species, 12 databases Visual Basic,C++ x86 Microsoft Windows
15. v7.1 2011 Public 22 modules, 25000 species, 12 databases Visual Basic,C++ x86 Microsoft Windows
16. v8.0 2014 Public 24 modules, 28000 species, 12 databases .NET Framework x86-64 Microsoft Windows

* Delivery to the other companies started

Calculation Modules

[edit]

All the HSC Chemistry calculation modules have been made to solve real practical problems in industrial processes or to decrease the amount of expensive trial-and-error chemistry in R&D work. HSC Chemistry contains 24 calculation modules which are connected to the 12 databases as appropriate[4]. Most calculation modules operate like independent programs which may have data links with each other. All the calculation modules have their own user interface and manual.

Reaction Module

[edit]

The Reaction module is used to analyze chemical reaction equilibrium and energy requirements. The reaction module also makes it possible to calculate dissolution heats and vapor pressures. The updated module has an illustrative and easy-to-use user interface, and comprehensive charting tools. The calculation results may be collected on several sheets which may be used to compare and visualize the results on the charts[7].

  • File extension: .rea8

Balance Module

[edit]

The Balance module is used to estimate the heat and material balances of one or more balance areas. The latest Balance module has an improved user interface and charting tools, as well as the new predictive chemical formula typing[8]. Users can modify the user interface according to their own requirements. The new updated module also calculates exergy balances[8].

  • File extension: .bal8

Heat Transfer Module

[edit]

The Heat Transfer module[9] estimates the heat losses and heat transfer of reactors for various geometries with given reactor walls and linings. It may therefore be a useful assistant during the thermal design of reactors. The ergonomics and visual appearance of the user interface have been improved in the latest HSC Heat Transfer version 8. The databases have been updated and expanded, and references have been added to the data. The new Specify Layer Type dialog makes the specification of layer properties much easier than earlier. Measurement unit changes have also been made easier.

  • File extension: .htr8

Equilibrium Module

[edit]

Gibbs equilibrium calculations[10] offer a practical way to investigate and study the effect of raw materials and process variables on the products of chemical reactors. This helps to estimate recoveries, opportunities and limits of sustainability. Calculations can be repeated at stepwise intervals over any entered range of raw material quantities or reaction temperatures in order to visualize the effect of these process variables. The Gibbs Energy Minimization (Gem) method is utilized in the calculations. This method was first introduced in W.B. White, S. M. Johnson, and G. B. Dntzig paper “Chemical Equilibrium in Complex Mixtures, The Journal of Chemical Physics, (May 1958)[11]

  • File extension: .gem8

Cell / Equilibrium Module

[edit]

The Cell module[10] calculations have been integrated into Gem. The Cell module uses the same Gibbs Energy Minimization routine as the main equilibrium module[10]. This makes it possible to calculate the phase compositions and cell voltages of electrochemical cells. This integration also enables plotting of 2D and 3D charts in electrochemical systems with the discharge level on x-axis.

  • File extension: .gem8

Aqua Module

[edit]

The Aqua module[12] contains non-ideal aqueous electrolyte models and databases. This module estimates a number of water solution properties, like activity coefficients, enthalpies, boiling point elevations, freezing point depressions, etc. as a function of composition and temperature. The Aqua module works as a standalone tool to calculate water solution properties, but it may also be utilized directly in the equilibrium module for water solutions[12].

  • File extension: .aqu8

Tpp Stability Diagrams Module

[edit]

The Tpp Diagram module calculates phase stability diagrams using partial pressures on both axes or with temperature on the x-axis and partial pressure on the y-axis[13]. This module calculates the diagram on the basis of minimum Gibbs energy[10].

  • File extension: .tpp8

Lpp Stability Diagrams Module

[edit]

The Lpp phase stability diagrams[14] show the stability areas of condensed phases in a ternary system in isothermal conditions, with the remaining constraints as the other axis. The Lpp Diagram module draws isothermal phase stability diagrams of three-element systems. These diagrams are also known as predominance area diagrams or Kellogg diagrams[14].

  • File extension: .lpp8

EpH Module

[edit]

E-pH-diagrams[15], also known as Pourbaix diagrams[16], show the thermodynamic stability areas of different species in water solutions. Stability areas are presented as a function of pH and electrochemical potential scales. Usually the upper and lower stability limits of water are also shown in the diagrams by dotted lines. The EpH module makes it possible to create diagrams in any temperature, concentration, and element combination. Traditional Pourbaix handbooks give these only for a very limited number of combinations[17][18][15].

  • File extension: .eph8

Diagrams Module

[edit]

The Diagram module[19] presents the basic thermochemical data for a given species in graphical format. Eight different diagram types can be drawn as a function of temperature. One of the most useful diagrams is the DG diagram[19][20] (Ellingham diagram). It shows the relative stability of various oxides, sulfates, chlorides, etc. as a function of temperature[19].

  • File extension: .dia8

Estimation Module

[edit]

The HSC Estimation module[21][22] gives a rough estimate of the H,S, and Cp values for any chemical species or non-stoichiometric mineral that exists in the HSC database[5], and also for those that do not exist in the HSC database. The Estimation module also gives the oxidation states of the elements in a given chemical compound[22].

Benson Estimation Module

[edit]

Benson estimation[23][24] is a new module which estimates the H,S, and Cp data of organic chemical compounds. It is also useful for estimating properties for complex mixed organic scrap, plastics, residues, etc. The number of chemical species is increasing rapidly[25], with over 90 million identified so far[23][25]. Estimation routines have an important role because 99.9% of the experimental H,S, and Cp are missing[25][23] .

  • File extension: .ben8

Water Module

[edit]

The Water calculator module[26] is a very useful replacement for steam table[27][28] books and Mollier diagrams[29] . Moreover, the Water module gives the enthalpies and other quantities using the same standard states as other HSC modules. By directly typing the pressure and temperature of the water system, or by simply clicking on the diagram, the process enthalpy and entropy are calculated along with several other useful thermodynamic data[26].

Measure Units Module

[edit]

Traditionally, several types of energy, temperature, mass, and volume units have been used in thermochemical calculations. Therefore, conversions are needed to compare results from different sources[30][31]. The Measure Units Conversion module[32] is an easy tool for fast unit conversions in thermochemistry as well as in other engineering fields. This module carries out an extensive number of measurement unit conversions[32].

Elements Module

[edit]

The Elements module [33]shows the 56 element properties in the database but also in graphical format. These properties can be easily edited, while new properties and additional data can be added. The Element module is not just a static Periodic table, but a dynamic one with visual effects and an editable database - very useful for visualizing and understanding the properties of elements[34].

Converter Module

[edit]

The Species Converter module[35] is a new, data reconciliation tool, which converts elemental analyses into any required species analyses and vice versa. It may also be applied to convert elements to non-stoichiometric[36] species. Usually chemical species are easy to convert to elements, but the reverse conversion from inaccurate experimental data is a much more challenging task. Three different solution methods are available.

Exergy Module

[edit]

This new HSC 8.0 Exergy module[37] calculates the exergies of chemical species and energy streams. These same calculation routines are utilized in many other HSC modules. Exergy analysis is used in industrial ecology to measure the amount of usable energy to create more sustainable processes[38].

HSC Database Module

[edit]

The HSC Database module[5][39][40][41][42][43][44][45][46][47][48] has versatile search and edit methods which are integrated into one powerful search dialog. Users can carry out various different searches based on elements, species, keywords, etc. The module has an attractive visual apprearance with a new predictive chemical formula typing system. Databases have been expanded from 25,000 to 28,000 chemical species[5]. The data of 1300 species have been updated.

Geo Module

[edit]

HSC Geo[49] is a collection of tools developed originally for geologists and mineralogists. However, these tools may also be useful for other professionals. HSC Geo offers an extensive database with data on 13,346 minerals. The Geo module has an intuitive user interface and versatile database tools which enable, for example, complex filtering criteria for the mineral database. The mineralogy calculation tool enables complex element/mineral conversions.

Help Module

[edit]

The Help module contains manuals for all HSC modules and databases; searches can be carried out for all the manuals using different keywords[1].

Sim Flowsheet Simulation Module

[edit]

The Sim module[50] is a multiform computing platform for many different types of process models[51]. The user can easily create Excel- or DLL-type customizable unit operation models and connect them with each other using a flowsheet. The Sim module also known as HSC Sim[52] may, for example, be used to create process models for hydrometallurgical and [[Pyrometallurgy|pyrometallurgical] systems as well as for mineral processing and physical recycling. Most of the HSC Chemistry modules have been made for the simulation of chemical reactions[53] in a single process unit. The HSC Sim module extends the scope to a whole process consisting of several process units. Modeling and simulation are the most important tools required when developing new processes and improving previous ones. Process calculations are the basis of the design, dimensioning, and sizing of reactors, plants, and systems. The economy, energy efficiency, environmental impact, and sustainable effects of the process are established in the modeling stage and therefore establish CAPEX and OPEX[50]. This stage also integrates disciplines, while harmonizing practices and enabling realistic environmental footprinting with valid material and energy balances. The Sim module has many useful features, including tools for LCA (Life Cycle Assessment) environmental footprint calculations, exergy calculations, distribution specifications, etc. The Sim module LCA tool makes it possible to estimate the ecobalances of processes by exporting data in formats accessible to 3rd party LCA software[50]. The Mass Balance module[54] helps to calibrate the theoretical process models with experimental data. The new converter unit makes it possible to convert a mineralogical materials stream to the stoichimetric chemical species needed in chemical process models.

  • File extension: .sim8

HSC Mass Balance Module

[edit]

Experimental process data usually requires harmonization by data reconciliation. Usually such data is incomplete and contains errors, which leads to problems when applying experimental data to process models. The Mass balance module[54] uses complex data reconciliation techniques to convert incomplete experimental process data to balanced data. This makes it possible to calibrate theoretical process models or simply to create consistent analyses for yield and efficiency estimates for complete energy and material flow systems. The Mass Balance module is connected to the HSC Sim module. The Sim Model Fit tool[55] enables the conversion of balanced experimental data into model parameters.

Sampler Module

[edit]

Sampler module can be used to calculate the size of the samples and to design sample preparation steps. Sampler solves sampling problems using P. Gy's equation[56][57]. Sampler has three separate calculation windows for calculating:

  • Number of nuggets in a sample
  • Error in single-stage sampling
  • Error in multistage sampling

With Sampler user can answer questions such as:

  • What is the primary sample size required?
  • What is the size of the secondary sample required?
  • How should I do the sample preparation (sample crushing, grinding and splitting)?

Map Module

[edit]

HSC Map[58] is location (GPS) based stock control software. HSC Map is designed for feed mixture calculation and raw material stock control. The basic idea is that the user may easily collect the raw materials from the stock and calculate a single or multi mixture composition, in order, for example, to obtain the proper copper and silica content and calorific value in the feed mixture. The user may also test the calculated feed mixtures using the HSC Sim[50] process simulator before starting to use the new mixture.

The material location data may be used in the HSC Map module, because most concentrates, fluxes and scrap materials look the same and the easiest way to identify them is the map location data. Valid location data decreases material searching time and also the number of various mistakes and errors when raw materials are transported in the stock field.

HSC Chemistry 8

[edit]

HSC Chemistry 8 is the latest HSC Chemistry version released on 31st october 2014.

HSC Main Menu – User Settings

[edit]

The modules and databases are accessed via a new dynamic main menu that can be customized by the user. It is easy to modify HSC Main menu user settings like in smart phones: images, colors, tile sizes, splash screens, etc.

Highlights

[edit]

HSC Excel Add-In Functions

[edit]

With HSC Add-In Functions[59] it is possible to use the HSC database and functions directly under HSC spreadsheet editors as well as under MS Excel. Add-In functions make it possible to carry out thermochemical and mineralogical calculations in Excel spreadsheets. More than 100 different add-in functions are available[1]. In the HSC Sim calculation module these add-in functions turn unit models into “small HSC engines”. For example: the StreamEQ function calculates the equilibrium composition for given raw materials and temperature[50]. Similar HSC internal functions may be called from your own .NET applications.

Predictive Formula Input

[edit]

The new predictive formula input helps find the available species from the database. All the available species are visible in a drop-down list box when the user types a formula[7].

Create models for unit operations

[edit]

The HSC Sim platform enables the user to create various Excel- or DLL-type unit operation models[50]. Predefined model templates have been divided into four categories (modes): Reaction, Distribution, Particles and Others. Drawing and many other features are similar in all unit modes and types.

Particle Mode
[edit]

Unit operation calculations are based on particle distributions. This mode is often used in minerals processing and physical recycling. Typical unit operations are crushing, grinding, flotation, gravity separation, and screening[50].

Reaction Mode
[edit]

Reaction mode unit operation calculations are based on chemical reactions, i.e. the process models are described by a relevant selection of chemical reaction equations[50]. The Reaction Mode unit editor contains Wizards to ease the development of the models. This mode is often used in hydrometallurgical processes.

Distribution Mode
[edit]

Distribution unit operation models are based on element distributions. This makes it possible to calibrate theoretical mass and energy balance models with experimental distribution data. This mode is often used in pyrometallurgical processes[50].

Sim - Environmental impact

[edit]

The LCA tool has been integrated into the HSC Sim module. This enables the real life-cycle analysis of the process. The Sim LCA tool automatically collects process input and output streams and calculates a few key indicators like carbon dioxide emissions. Sim process models are based on material and energy balances; this automacally leads to thermodynamically accurate ecobalances. This is the main advantage of Sim-based ecobalances over conventional LCA methods, which often do not meet critical element and energy balance boundary conditions. Environmental impact assessment in HSC Sim 8 combines the simulation functionality of HSC Sim with the functionality of third party environmental impact assessment software[50], like GaBi[60]. This provides a rigorous mass and energy balance as well as a techno-economic basis for LCA and thus links environmental impact analysis to technology. The LCA tool makes it possible to optimize the whole process not only from the technical and economic point of view, but also taking into account the environmental impact. This must be done in the process design stage, because later on in the engineering, construction, and start-up stages this is too late and very expensive.

Printscreen images

[edit]

See Also

[edit]

Citations

[edit]

Some publications where HSC Chemistry has been utilized/Cited can be viewed here[61].

References

[edit]
  1. ^ a b c d e f g h i j k "HSC Chemistry". Outotec. Retrieved 2014-12-04.
  2. ^ a b "Outotec History". Outotec. Retrieved 2014-12-05.
  3. ^ "System Requirements". Outotec. Retrieved 2014-12-04.
  4. ^ a b "Calculation Modules". Outotec. Retrieved 2014-12-05.
  5. ^ a b c d e "HSC Chemistry databases". Outotec. Retrieved 2014-12-05.
  6. ^ "Outotec Research center, Pori". Outotec. Retrieved 2014-12-05.
  7. ^ a b "Reaction Module". Outotec. Retrieved 2014-12-05.
  8. ^ a b "Balance Module". Outotec. Retrieved 2014-12-05.
  9. ^ "Heat Transfer Module". Outotec. Retrieved 2014-12-05.
  10. ^ a b c d "Equilibrium Module". Outotec. Retrieved 2014-12-05.
  11. ^ W.B. White, S. M. Johnson, and G. B. Dntzig: Chemical Equilibrium in Complex Mixtures, The Journal of Chemical Physics, May 1958
  12. ^ a b "Aqua Module". Outotec. Retrieved 2014-12-05.
  13. ^ "Tpp Module". Outotec. Retrieved 2014-12-05.
  14. ^ a b "Lpp Module". Outotec. Retrieved 2014-12-05.
  15. ^ a b "EpH Module". Outotec. Retrieved 2014-12-05.
  16. ^ "Pourbaix diagram". Wikipedia. Retrieved 2014-12-05.
  17. ^ "Marcel Pourbaix". Wikipedia. Retrieved 2014-12-05.
  18. ^ "Predominance diagram". Wikipedia. Retrieved 2014-12-05.
  19. ^ a b c "Diagrams Module". Outotec. Retrieved 2014-12-05.
  20. ^ "Ellingham diagram". Wikipedia. Retrieved 2014-12-05.
  21. ^ H Nyman, T Talonen, A Roine, M Hupa, and J Corander: Statistical Approach to Quality Control of Large Thermodynamic Databases. October 2012, Volume 43, Issue 5, pp 1113-1118
  22. ^ a b "Estimation Module". Outotec. Retrieved 2014-12-05.
  23. ^ a b c "Benson Estimation Module". Outotec. Retrieved 2014-12-05.
  24. ^ "Heat of formation group additivity". Wikipedia. Retrieved 2014-12-05.
  25. ^ a b c "Benson group increment theory". Wikipedia. Retrieved 2014-12-05.
  26. ^ a b "Water Module". Outotec. Retrieved 2014-12-05.
  27. ^ Lange, p. 1476
  28. ^ "Water (data page)". Wikipedia. Retrieved 2014-12-05.
  29. ^ "Enthalpy–entropy chart". Wikipedia. Retrieved 2014-12-05.
  30. ^ "International System of Units". Wikipedia. Retrieved 2014-12-05.
  31. ^ "SI base unit". Wikipedia. Retrieved 2014-12-05.
  32. ^ a b "Measure Units Module". Outotec. Retrieved 2014-12-05.
  33. ^ "Elements Module". Outotec. Retrieved 2014-12-05.
  34. ^ "List of elements". Wikipedia. Retrieved 2014-12-05.
  35. ^ "Converter Module". Outotec. Retrieved 2014-12-05.
  36. ^ "Stoichiometry". Wikipedia. Retrieved 2014-12-05.
  37. ^ "Exergy Module". Outotec. Retrieved 2014-12-05.
  38. ^ "Exergy efficiency". Wikipedia. Retrieved 2014-12-05.
  39. ^ "HSC Thermochemical". Outotec. Retrieved 2014-12-05.
  40. ^ "Water Steam/Fluid Database". Outotec. Retrieved 2014-12-05.
  41. ^ "Heat-Conduction Database". Outotec. Retrieved 2014-12-05.
  42. ^ "Heat-Convection Database". Outotec. Retrieved 2014-12-05.
  43. ^ "Surface-radiation Database". Outotec. Retrieved 2014-12-05.
  44. ^ "Elements Database". Outotec. Retrieved 2014-12-05.
  45. ^ "Measure-units Database". Outotec. Retrieved 2014-12-05.
  46. ^ "Minerals Database". Outotec. Retrieved 2014-12-05.
  47. ^ "Aqueous-solution-density Database". Outotec. Retrieved 2014-12-05.
  48. ^ "Pitzer-parameter Database". Outotec. Retrieved 2014-12-05.
  49. ^ "Geo Module". Outotec. Retrieved 2014-12-05.
  50. ^ a b c d e f g h i j "Sim Flowsheet Simulation Module". Outotec. Retrieved 2014-12-05.
  51. ^ "Chemical process modeling". Wikipedia. Retrieved 2014-12-05.
  52. ^ "List of chemical process simulators". Wikipedia. Retrieved 2014-12-05.
  53. ^ "Process simulation". Wikipedia. Retrieved 2014-12-05.
  54. ^ a b "Mass Balance Module Module". Outotec. Retrieved 2014-12-05.
  55. ^ "FIT - Numerical data fit". Outotec. Retrieved 2014-12-05.
  56. ^ Gy, P (2004), Chemometrics and Intelligent Laboratory Systems, 74, 61-70.
  57. ^ "Gy's sampling theory". Wikipedia. Retrieved 2014-12-05.
  58. ^ "HSC Map Module". Outotec. Retrieved 2014-12-05.
  59. ^ "HSC Excel Add-In Functions". Outotec. Retrieved 2014-12-05.
  60. ^ UNEP SETAC (2011). Global Guidance Principles for Life Cycle Assessment Databases. http://www.unep.fr/shared/publications/pdf/DTIx1410xPA-GlobalGuidancePrinciplesforLCA.pdf: United Nations Environment Program. {{cite book}}: External link in |location= (help)CS1 maint: location (link)
  61. ^ "HSC chemistry Citation list" (PDF). Outotec. Retrieved 2014-12-05.
[edit]
Retrieved from "https://en.wikipedia.org/w/index.php?title=User:Bsalonline/HSC_Chemistry&oldid=641990191"