Wiktionary
potash alum
n. alum, hydrated potassium aluminium sulphate, formula K2SO4.Al2(SO4)3.24H2O
WordNet
potash alum
n. a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum [syn: alum, potassium alum]
Usage examples of "potash alum".
I used eggshells, sulfur, vitriol, arsenic, sal ammoniac, quartz, alkalis, oxides of rock, saltpeter, soda, salt of tartar, and potash alum.