Editing Calorimeter (section)

==Differential scanning calorimeter==
{{main article|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate 
: ''dT''/''dt'' = ''β''
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''C''<sub>p</sub>. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

: <math>\Delta T = K {dq \over dt} = K C_\text{p}\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
: {{math|1=Δ''V'' = ''R{{sfrac|dQ|dt}}'' = ''RI''}}.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

: <math>{dq \over dt} = C_\text{p} \beta + f(t, T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that respond to a changing heating rate (reversing) and that don't respond to the changing heating rate (non-reversing). It allows for the optimization of both sensitivity and resolution in a single test by allowing for a slow average heating rate (optimizing resolution) and a fast changing heating rate (optimizing sensitivity).<ref>{{Cite web |url=http://csacs.mcgill.ca/francais/docs/CHEM634/DSC_Hunt.pdf |title=Archived copy |access-date=2014-07-25 |archive-url=https://web.archive.org/web/20140729025301/http://csacs.mcgill.ca/francais/docs/CHEM634/DSC_Hunt.pdf |archive-date=2014-07-29 |url-status=dead }}</ref>

A DSC may also be used as an initial safety screening tool.  In this mode the sample will be housed in a non-reactive crucible (often [[gold]], or gold-plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2–3&nbsp;°C per min) due to much heavier crucible, and unknown [[activation energy]], it is necessary to deduct about 75–100&nbsp;°C from the initial start of the observed exotherm to suggest a maximum temperature for the material.  A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3&nbsp;°C increment per half hour.