Tollens' reagent can also be used to test for terminal alkynes ( R − C 2 H {\displaystyle {\ce {R-C2H}}} ). A white precipitate of the acetylide ( AgC − R {\displaystyle {\ce {AgC-R}}} ) is formed in this case. Another test relies on reaction of the furfural with phloroglucinol to produce a colored compound with high molar absorptivity.[4] It also gives a positive test with hydrazines, hydrazones, α-hydroxy ketones and 1,2-dicarbonyls.