Molecular Weight Calculator(計算化學運算式的分子量)

問題

最近有個需求要將化學運算式字串算出它的分子量是多少，例如，

CaCO3 => 100.0869
CO2 => 44.0095
CO2 / CaCO3 => 0.4397
2 * CO2/C2H2 => 3.380499038
C2H2 +2.5 * O2 => 106.03428

解法

為什麼 CaCO3 的分子量是 100.0869 呢?
可以從Molecular Weight Calculator發現，
它是Calcium(40.078) + Carbon(12.0107) + Oxygen(15.9994)*3，
所以總共分子量是 40.078 + 12.0107 + 47.9982 = 100.0869

處理拆分成四步

1. 找出運算式中的變數(CO2, CaCO3 …)
2. 計算出這些變數的值(加總)
3. 指定將運算式中變數的值
4. 計算出運算式的結果

1.找出運算式中的變數，可透過ncalc的Expression.Compile來幫忙，

var ec = Expression.Compile(expression, false);
ParameterExtractionVisitor visitor = new ParameterExtractionVisitor();
ec.Accept(visitor);
var extractedParameters = visitor.Parameters;

internal class ParameterExtractionVisitor : LogicalExpressionVisitor
{
    public HashSet<string> Parameters = new HashSet<string>();
    public override void Visit(NCalc.Domain.Identifier function)
    {
        //Parameter - add to list
        Parameters.Add(function.Name);
    }
    public override void Visit(NCalc.Domain.UnaryExpression expression)
    {
        expression.Expression.Accept(this);
    }
    public override void Visit(NCalc.Domain.BinaryExpression expression)
    {
        //Visit left and right
        expression.LeftExpression.Accept(this);
        expression.RightExpression.Accept(this);
    }
    public override void Visit(NCalc.Domain.TernaryExpression expression)
    {
        //Visit left, right and middle
        expression.LeftExpression.Accept(this);
        expression.RightExpression.Accept(this);
        expression.MiddleExpression.Accept(this);
    }

    public override void Visit(LogicalExpression expression)
    {
    }
    public override void Visit(ValueExpression expression)
    {
    }

    public override void Visit(NCalc.Domain.Function function)
    {
        foreach (var expression in function.Expressions)
        {
            expression.Accept(this);
        }
    }
}

2.計算出這些變數的值(加總)，可以透過正則表達式匹配元素及其數量，並計算出分子量總和

double CalcMolecularFormulaMass(string formula)
{
    // 使用正則表達式匹配元素及其數量
    string pattern = @"([A-Z][a-z]*)(\d*)";
    MatchCollection matches = Regex.Matches(formula, pattern);
    double totalFormulaWeight = 0;
    foreach (Match match in matches)
    {
        string element = match.Groups[1].Value;
        int count = match.Groups[2].Value == "" ? 1 : int.Parse(match.Groups[2].Value);
        try
        {
            var atomicWeight = _MolecularWeights[element];
            var formulaWeight = atomicWeight * count;
            totalFormulaWeight += formulaWeight;
        }
        catch(KeyNotFoundException)
        {
            throw new KeyNotFoundException($"'{element}' was not present in the Periodic Table");
        }catch(Exception)
        {
            throw;
        }
    }
    return totalFormulaWeight;
}

然後建立元素分子量對應表，讓CalcMolecularFormulaMass可以取到每個元素的分子量，

private static IReadOnlyDictionary<string, double> _MolecularWeights
    = new Dictionary<string, double>
        {
            {"H", 1.0080}, //Hydrogen
            {"He", 4.0026}, //Helium
            {"Li", 6.94}, //Lithium
            {"Be", 9.0122}, //Beryllium
            {"B", 10.81}, //Boron
            {"C", 12.011}, //Carbon
            {"N", 14.007}, //Nitrogen
            {"O", 15.999}, //Oxygen
            {"F", 18.998}, //Fluorine
            {"Ne", 20.180}, //Neon
            {"Na", 22.990}, //Sodium
            {"Mg", 24.305}, //Magnesium
            {"Al", 26.982}, //Aluminum
            {"Si", 28.0855}, //Silicon
            {"P", 30.974}, //Phosphorus
            {"S", 32.06}, //Sulfur
            {"Cl", 35.45}, //Chlorine
            {"Ar", 39.95}, //Argon
            {"K", 39.098}, //Potassium
            {"Ca", 40.078}, //Calcium
            {"Sc", 44.956}, //Scandium
            {"Ti", 47.867}, //Titanium
            {"V", 50.942}, //Vanadium
            {"Cr", 51.996}, //Chromium
            {"Mn", 54.938}, //Manganese
            {"Fe", 55.845}, //Iron
            {"Co", 58.933}, //Cobalt
            {"Ni", 58.693}, //Nickel
            {"Cu", 63.546}, //Copper
            {"Zn", 65.38}, //Zinc
            {"Ga", 69.723}, //Gallium
            {"Ge", 72.630}, //Germanium
            {"As", 74.922}, //Arsenic
            {"Se", 78.971}, //Selenium
            {"Br", 79.904}, //Bromine
            {"Kr", 83.798}, //Krypton
            {"Rb", 85.468}, //Rubidium
            {"Sr", 87.62}, //Strontium
            {"Y", 88.906}, //Yttrium
            {"Zr", 91.224}, //Zirconium
            {"Nb", 92.906}, //Niobium
            {"Mo", 95.95}, //Molybdenum
            {"Tc", 97}, //Technetium
            {"Ru", 101.07}, //Ruthenium
            {"Rh", 102.91}, //Rhodium
            {"Pd", 106.42}, //Palladium
            {"Ag", 107.87}, //Silver
            {"Cd", 112.41}, //Cadmium
            {"In", 114.82}, //Indium
            {"Sn", 118.710}, //Tin
            {"Sb", 121.760}, //Antimony
            {"Te", 127.60}, //Tellurium
            {"I", 126.90}, //Iodine
            {"Xe", 131.29}, //Xenon
            {"Cs", 132.91}, //Caesium
            {"Ba", 137.33}, //Barium
            {"La", 138.91}, //Lanthanum
            {"Ce", 140.12}, //Cerium
            {"Pr", 140.91}, //Praseodymium
            {"Nd", 144.24}, //Neodymium
            {"Pm", 145}, //Promethium
            {"Sm", 150.36}, //Samarium
            {"Eu", 151.96}, //Europium
            {"Gd", 157.25}, //Gadolinium
            {"Tb", 158.93}, //Terbium
            {"Dy", 162.50}, //Dysprosium
            {"Ho", 164.93}, //Holmium
            {"Er", 167.26}, //Erbium
            {"Tm", 168.93}, //Thulium
            {"Yb", 173.05}, //Ytterbium
            {"Lu", 174.97}, //Lutetium
            {"Hf", 178.49}, //Hafnium
            {"Ta", 180.95}, //Tantalum
            {"W", 183.84}, //Tungsten
            {"Re", 186.21}, //Rhenium
            {"Os", 190.23}, //Osmium
            {"Ir", 192.22}, //Iridium
            {"Pt", 195.08}, //Platinum
            {"Au", 196.97}, //Gold
            {"Hg", 200.59}, //Mercury
            {"Tl", 204.38}, //Thallium
            {"Pb", 207.2}, //Lead
            {"Bi", 208.98}, //Bismuth
            {"Po", 209}, //Polonium
            {"At", 210}, //Astatine
            {"Rn", 222}, //Radon
            {"Fr", 223}, //Francium
            {"Ra", 226}, //Radium
            {"Ac", 227}, //Actinium
            {"Th", 232.04}, //Thorium
            {"Pa", 231.04}, //Protactinium
            {"U", 238.03}, //Uranium
            {"Np", 237}, //Neptunium
            {"Pu", 244}, //Plutonium
            {"Am", 243}, //Americium
            {"Cm", 247}, //Curium
            {"Bk", 247}, //Berkelium
            {"Cf", 251}, //Californium
            {"Es", 252}, //Einsteinium
            {"Fm", 257}, //Fermium
            {"Md", 258}, //Mendelevium
            {"No", 259}, //Nobelium
            {"Lr", 262}, //Lawrencium
            {"Rf", 267}, //Rutherfordium
            {"Db", 268}, //Dubnium
            {"Sg", 269}, //Seaborgium
            {"Bh", 270}, //Bohrium
            {"Hs", 269}, //Hassium
            {"Mt", 277}, //Meitnerium
            {"Ds", 281}, //Darmstadtium
            {"Rg", 282}, //Roentgenium
            {"Cn", 285}, //Copernicium
            {"Nh", 286}, //Nihonium
            {"Fl", 290}, //Flerovium
            {"Mc", 290}, //Moscovium
            {"Lv", 293}, //Livermorium
            {"Ts", 294}, //Tennessine
            {"Og", 294}, //Oganesson
        };

3.指定將運算式中變數的值及 4.計算出運算式的結果，可以再透過ncalc的Expression來幫忙，

var e = new Expression(ec);
foreach (var param in extractedParameters)
{
    double paramValue = CalcMolecularFormulaMass(param);
    e.Parameters[param] = paramValue;
}
var result = e.Evaluate();

以上的內容筆者已放到 Nuget 之中，可以安裝MolecularWeightCalculator套件，直接使用即可。

var molecularMath = new MolecularMath();
string exp1 = "CO2";
var exp1Result = molecularMath.ComputeMass(exp1);
Console.WriteLine($"{exp1}=>{exp1Result}");
//CO2=>44.009

string exp2 = "CaCO3";
var exp2Result = molecularMath.ComputeMass(exp2);
Console.WriteLine($"{exp2}=>{exp2Result}");
//CaCO3=>100.086

string exp3 = "CO2 / CaCO3";
var exp3Result = molecularMath.ComputeMass(exp3);
Console.WriteLine($"{exp3}=>{exp3Result}");
//CO2 / CaCO3=>0.43971184781088263

string exp4 = "C2H2 +2.5 * O2";
var exp4Result = molecularMath.ComputeMass(exp4);
Console.WriteLine($"{exp4}=>{exp4Result}");
//C2H2 +2.5 * O2=>106.033


string exp5 = "2*CO2/C2H2";
var exp5Result = molecularMath.ComputeMass(exp5);
Console.WriteLine($"{exp5}=>{exp5Result}");
//2*CO2/C2H2=>3.3803671556955224

string exp6 = "1*2*3*4";
var exp6Result = molecularMath.ComputeMass(exp6);
Console.WriteLine($"{exp6}=>{exp6Result}");
//1*2*3*4=>24

string exp7 = "CaCO3 * A2 + B3";
//var exp7Result = molecularMath.ComputeMass(exp7);
//Console.WriteLine($"{exp7}=>{exp7Result}");
//KeyNotFoundException: 'A' was not present in the Periodic Table

程式碼放請參考MolecularWeightCalculator Source

參考資源

MolecularWeightCalculator Source
Molecular Weight Calculator
ncalc
IUPAC_Periodic_Table_150-04May22.jpg

一尺青天，蓋一尺土: 每個人都有自己的天地，每個人都有自己的生活方式