Re: Calorimetry is alive and well

[trappe@PHYSICS.UTEXAS.EDU (Karl Trappe)]

Hear, Hear for Timothy Folker!

It does my heart good to hear a diehard heat capacity measuring, solid
state (now condensed matter) physicist defend his trade.

The phase transition heat capacity of the Perovskites were being measured
long before they were known to be an ideal structure for high Tc
superconductors.

I redid SrTiO3 in the 70's along with KMnF3, taking milidegree increments
(each half hour or so) over tens of degrees of range.  That may be proof
enough, however that such measurements are "outmoded".  But Timothy, you
warm the cockles of my heart...Karl

> > > However, I do believe
> > > that there is justification in teaching calorimetry  as an outmoded
> > > concept that has historical significance and has helped science progress.
> >
> > In its modern usage, 'calorimetry' has *nothing*
> > to do with 'caloric' the non-existant substance (except etymologically).
> Quite true.  Calorimetry - heating something and watching what
> happens to the temperature - is still alive and well in solid state
> physics, as well as in chemistry.  The specific heat of a material, as
> well as latent heats from _any_ phase transition provide valuable
> insights into materials.
>
> For example, when a material is cooled and undergoes a phase change
> from non-superconducting to superconducting, the specific heat changes
> in a way that clearly indicates that it has become superconducting.
> The specific heat of a piece of glass can even tell you if it was
> cooled slowly or quenched rapidly!
>
>
> > * I say 'usually' because I believe that there are more complicated set ups
> > in use these days.  A search on the WWW brought up pages on things like
> > 'differential scanning calorimetry', whatever that is.
>
> FYI:
> Think of differential scanning calorimetry as two simultaneous
> calorimetry experiments.  A know quantity of a known material (like
> Al2O3 or quartz) is heated at a constant rate.  A second material to be
> studied is simultaneously heated at the same rate.  As the heat is
> applied, the temperatures increases (hence "scanning").  The difference
> between the temperatures of the two objects (hence "differential") is
> related to their specific heats (hence "calorimetry").  If the specific
> heat of the first is known, the second can be easily determined.  This
> is particularly useful at either high or low temperatures, where it is
> hard to thermally isolate the sample from its surroundings
>
> Tim
>
>
> ----------------------
> Timothy J. Folkerts            email:  tim.folkerts@valpo.edu
> Department of Physics          phone:  219-465-2134
> Valparaiso University
> Valparaiso, IN  46383

Dr. Karl I. Trappe                              Desk Phone:  (512) 471-4152
Physics Dept, Mail Stop C-1600                  Demo Office: (512) 471-5411
The University of Texas at Austin               Home Phone:  (512) 264-1616
Austin, Texas 78712-1081