How to calculate the heat capacity value from DSC graph (i.e. J/kG- K versus temperature (K)?
In DSC software (for example Universal analysis for TA) has option either you can get the data by heat flow or enthalpy provided your instrument. Otheriwse you can calculate mathematically.
Mathematically it is the heat flow divided by the heating rate. Here are links to two papers that explaina procedure:
http://cis01.central.ucv.ro/pauc/vol/2013_23/PAUC_2013_89_94.pdf
http://www.tpl.fpv.ukf.sk/engl_vers/thermophys/proceedings/simon.pdf
To get precise value you typically perform several measurements with the same temperature program. According to standards it is the following procedure:
starting with a empty crucible you get a base line for your equipment which can be substracted from your following measurments.
then measuring a sapphire (every other well known material will also work, but you can buy well defined sets of sapphire reference samples) reference sample in the same crucible and finally your sample.
As sapphire has a well known heat capacity you can calculate your desired heat capacity of your sample.
It is helpful if your sapphire sample has a suitable mass to ensure that the heat uptake of the sapphire is comparable to the heat uptake of your sample to eliminate/reduce experimental effects.
Additionally you should ensure that no chemical reactions or physical transitions take place in your sample within the temperature range of your analysis.
I hope this procedure is useful.
regards
Matthias
Of course some DSC equipment is so well defined that you could directly follow the procedure mentioned by Thomas Trezza. This will always give you at least a good estimate which is often sufficient for comparison.
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