Titration of Butyl Lithium-I

2,2’-bipyridine (~5 mg) was dissolved in 3 mL of dry ether. n-Butyllithium in hexanes (50 μL) was added, such that a deep red color persisted. A 1.00 M solution of dry 2-butanol in benzene was added dropwise until the color dissipated, forming the yellow dihydropyridine indicator.

n-Butyllithium in hexanes (100 μL) was added to the indicator solution, turning it red. The 2-butanol solution was then added dropwise until the solution turned back to yellow. 

The concentration of butyllithium can be determined by dividing the amount of 2-butanol solution used by 100 μL (the amount of n-butyllithium solution used)

Source :  Ireland, R. E.; Meissner, R. S.  J. Org. Chem, 1991, 56, 4566.