Hi all,
I am looking for references about measuring crystallisation and metling enthalpy of pure water with differential scanning calorimetry (DSC).
Although this seems to be quite a straightforward job, are there any challenges associated with it?
Moreover, how can the presence of ions/proteins/biological membrane fragments, dissolved in water, affect the enthalpy of those phase transitions?
With many thanks
Best
Filippo
Dear Filippo Bramante, in the attached file, the thermogram of pure water is given with a labelled scales, I think you can deduce the enthalpies. My Regards
Many thanks Abdelkader BOUAZIZ and Tenzin Ingsel
for your useful answers.On measuring water, I obtain an enthalpy value on cooling (cooling rates 2,5, or 10°C/min) of 333±2 J/g, which is expected for pure water. However, enthalpy on melting (heating rates 2,5, or 10°C/min) is about 350-360 J/g, which seems to be slightly too high. I used Milli-Q water (18.2 MΩ·cm) so I do not expect any sample effect.
Would this increase in enthalpy take into account the fact that temperature is increasing in portions of water already melted, by the time phase transition is completed? I hope that makes sense.
With many thanks
Best wishes,
Filippo
Yes exactly, and it is well explained in one of the attached files. It adds also that the induction of crystals formation for sure will not be the same as in the reference enthalpy you refered to, because of many factors. This may include the environmental conditions, the instrument used and its accuracy (expected high compared to old instruments), the specimen holder (nature and geometrical form), and possibly others, all contribute to the obtained values. However as a general view, the values are not so far from each other. Good Luck in your work
Thank you Abdelkader BOUAZIZ, enlightening.
Good luck with your work too.
Best wishes
Filippo
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