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CHN Calculator Instructions

Heriot-Watt University
EPS - Chemistry

Calculator for CHN analysis

Copyright ©2000 Gareth Evans


Instructions for %CHN calculator

The calculator uses two field types -

  1. The element symbol box - (e.g. C, H, N, Na, Cl, O, S ....)
  2. The element quantity box - (0, 1, 2, 3 ....)

These fields appear on the screen as you would see an empirical formula written. e.g.


Element symbol box

Element quantity box

The above information would be entered if you were calculating %CHN values for 4-chlorobenzoic acid.

If you have elements other than C,H and N present, you can enter their symbols into the empty element symbol boxes, and the quantity of these elements in the empty element quantity boxes. When you have finished entering your required formula, click on the Click here to check results button to finalise the calculation and recheck your results.

Your theortical results are updated whenever you change one of the fields (i.e. when you enter a new value and move to the next field, or when you click on the 'Check' button).

Points to note

  • You can use the mouse or TAB button to select fields to enter required information

  • If you don't have C, H, or N in your compound, then enter 0 in their element quantity boxes. Also, if there is only one 'atom' of an element per formula, you must enter 1 in the element quantity box. Do not leave it blank.

    Although Ethanol, for example, has the formula CH3CH2OH, or C2H6O , when entering on the %CHN calculator, you must enter C2H6N0O1.

  • When entering 'other' elements -
    1. Do not use C, H or N.
    2. Elements can be entered in any order
    3. Element symbols are case sensitive - e.g. for Chlorine, you must use Cl and not cl or CL.
    4. Fields that are entered incorrectly (element symbols and quantities) are ignored in the calculations.

  • When using the calculator to complete your analysis request form, please quote your theoretical values to 2 decimal places.

%CHN calculator

Link to Heriot-Watt Elemental Analysis Home Page

Please contact  Dr Brian Hutton   for further information.