  Differential thermal analysis on metallic alloys containing volatile elements
can be highly problematic. Here we show how measurements can be performed in
commercial, small-sample, equipment without modification. This is achieved by
using a sealed Ta crucible, easily fabricated from Ta tubing and sealed in a
standard arc furnace. The crucible performance is demonstrated by measurements
on a mixture of Mg and MgB$_2$, after heating up to 1470$^{\circ}{\rm C}$. We
also show data, measured on an alloy with composition Gd$_{40}$Mg$_{60}$, that
clearly shows both the liquidus and a peritectic, and is consistent with
published phase diagram data.
