  Part I shows that quantitative measurements of heat capacity are
theoretically possible inside diamond anvil cells via high-frequency Joule
heating (100 kHz to 10 MHz), opening up the possibility of new methods to
detect and characterize transformations at high-pressure such as the glass
transitions, melting, magnetic orderings, or the onset of superconductivity.
Here we test the possibility outlined in Part I, using prototypes and detailed
numerical models. First, a coupled electrical-thermal numerical model shows
that specific heat of metals inside diamond cells can be measured directly
using $\sim 1$ MHz frequency, with $< 10%$ accuracy. Second, we test physical
models of high-pressure experiments, i.e. diamond-cell mock-ups. Metal foils of
2 to 6 $\mu$m-thickness are clamped between glass insulation inside diamond
anvil cells. Fitting data from 10 Hz to $\sim 30$ kHz, we infer the specific
heat capacities of Fe, Pt and Ni with $\pm 20$ to $30%$ accuracy. The
electrical test equipment generates -80 dBc spurious harmonics which overwhelm
the thermally-induced harmonics at higher frequencies, disallowing the high
precision expected from numerical models. An alternative Joule-heating
calorimetry experiment, on the other hand, does allow absolute measurements
with $< 10%$ accuracy, despite the -80 dBc spurious harmonics: the measurement
of thermal effusivity, $\sqrt{\rho c k}$ ($\rho$, $c$ and $k$ being density,
specific heat and thermal conductivity), of the insulation surrounding a
thin-film heater. Using a $\sim 50$ nm-thick Pt heater surrounded by glass and
10 Hz to 300 kHz frequency, we measure thermal effusivity with $\pm 6%$
accuracy inside the sample chamber of a diamond anvil cell.
