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- Exact Mass Calculator, Single Isotope Version (This Page)
This is a very primitive exact mass calculator. Given the formula of a chemical species, the calculator determines the exact mass of a single isotope of that species and the relative abundance of that isotope. The isotope selected has the property that each atom in the species is the most abundant isotope of that element. For low mass chemical species, the chosen isotope is often the most abundant isotope of the species; however, this is often not the case for larger mass species due to the need for a more complex algorithm to make such a determination.
How to input chemical formulas
Chemical formulas can be inputted according to a straightforward syntax. Include no spaces in input. Element names are case sensitive. Express formulas in terms of atoms (functional group abbreviations are not supported).Examples:
CH3COOH is written as CH3COOH
H2SO4 is written as H2SO4
Mg(OH)2 is written as Mg(OH)2
The architecture of the program can be understood in terms of compiler theory. The program first retrieves the chemical formula as a character string. This string is fed into a lexer, which converts the character string into a stream of tokens (e.g. atom names, numbers, and parenthesis). Invalid tokens (e.g. "Zy" or "%") produce an error. The parser sequentially reads tokens from the token stream. The parser is implemented as a state-machine, and the state of the parser changes as a function of the current parser state and the current token being read. By limiting the set of valid tokens at each state, the parser get make a distinction between syntactically valid (e.g. "Mg(OH)2") and syntactically invalid (e.g. ")MgO(H2") formulas. Note however that a syntactically valid formula ("CH6") is not necessarily semantically valid; this program makes no effort in determining semantic validity. During the parse phase, calculations are performed (i.e. generated). It is convenient that the parse and the generation phases can be closely coupled.
The mathematics is handled according to the following principle. An isotope of the form aAbB, where A and B are functional groups, themselves isotopes, has a mass of a + b and an fractional abundance equal to the product of the fractional abundances of the given functional group isotopes in their respective functional groups. The problem can be solved by recursion.
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Data is obtained from the CRC Handbook of Chemistry and Physics.
Disclaimer: Scientific Instrument Services is not responsible for any errors which may result from the use of this program.