Alkaline-earth halides can be made into bright scintillators if purity is maintained during synthesis and growth. In order
to investigate precursor purity, beaded halide precursors were heated under vacuum and evolved gas was assessed by
residual gas spectroscopy. These precursors included cesium chloride, lithium chloride, yttrium chloride, cerium
chloride, strontium iodide, europium iodide, barium bromide, and europium bromide. Water and CO2 desorption, sulfur release, argon release, and halide dissociation was observed in samples. Triply-oxidized precursors showed multiple
paths to decomposition. The data inform approaches toward purification and growth.