a white, crystalline salt, Na(NH)HPO·4HO, used as a reagent in blowpipe analysis because it forms characteristically colored compounds when fused with salts and oxides of metals
See microcosmic salt in American Heritage Dictionary 4
noun
A white crystalline salt of phosphorus, HNaNH4PO4·4H2O, used in blowpipe analysis of minerals to test for the presence of certain metals.