Can anyone help me calculate the heat of fusion in a DSC curve with the example please? Can anyone tell me how to calculate heat of crystallization in this figure?
you need to integrate the curves. note the following:
1 watt = 1 J/s ; enthalpy ( heat of fusion) is in J/kg
so first separate your heating and cooling curves. Then, zero the data from the heating/cooling runs so that the start of the transformation (at the transformation temperature) is zero. Achieve this by simply adding or subtracting a constant from the entire data set.
next, convert your mW data to watts (multiply by 1000) and divide the data by the mass of your sample (i.e. you want W/kg - which is the same as J/s*kg). then divide the data by the constant heating/cooling rate used in the DSC in Kelvin/sec - or Kelvin/min but convert min. to sec.) This would give you units of J/K*kg. Next, integrate the data from the start the end of the peak (transformation start to transformation finish temperatures), thus yielding the heat of fusion, H = int(Cp/T)dT from start to finish of transformation.
Most DSC software has a feature that will perform this integral for you. Otherwise, I would suggest using IGOR graphing software or some other form of data analysis.
you need to integrate the curves. note the following:
1 watt = 1 J/s ; enthalpy ( heat of fusion) is in J/kg
so first separate your heating and cooling curves. Then, zero the data from the heating/cooling runs so that the start of the transformation (at the transformation temperature) is zero. Achieve this by simply adding or subtracting a constant from the entire data set.
next, convert your mW data to watts (multiply by 1000) and divide the data by the mass of your sample (i.e. you want W/kg - which is the same as J/s*kg). then divide the data by the constant heating/cooling rate used in the DSC in Kelvin/sec - or Kelvin/min but convert min. to sec.) This would give you units of J/K*kg. Next, integrate the data from the start the end of the peak (transformation start to transformation finish temperatures), thus yielding the heat of fusion, H = int(Cp/T)dT from start to finish of transformation.
Most DSC software has a feature that will perform this integral for you. Otherwise, I would suggest using IGOR graphing software or some other form of data analysis.
To know the heat of crystallization knowledge of sample weight is prerequisite
The DSC software will do the needful else
calculate the area under the curve and do as mentioned in Bruno`s explination
Goodluck
thanks for your useful suggestions Mr. N. M. Bruno and Mr. M. L. N. Madhu Mohan.
N. M. Bruno are you sure that to convert from mW by multiplied by 1000?
i think mW meaning milliwatt so you must divide by 1000
Yes, the procedure I listed can be followed but the units must be consistent. If I messed up a conversion, please make sure it makes sense.
Dear Nickolaus M. Bruno, may I know why H = int(Cp/T)dT since we are integrating Cp only after all the conversion of data into final unit J/K*kg (the Cp)?
Thanks in advance!
Dear Sin Yee Lee.
Please watch this video
https://www.youtube.com/watch?v=wY7ewg3MrkE
i hope its useful to you.
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