Zinc uranyl acetate is sometimes called "sodium reagent"  since pale yellow NaZn(UO2)3(C2H3O2)9 is one of the very few insoluble sodium compounds.
Zinc uranyl acetate is occasionally called a "sodium agent" due to its unique property of being an insoluble sodium compound, exemplified by the pale yellow NaZn(UO2)3(C2H3O2)9.