Yol. 25 contained 2% of sodium. The mixture was stirred and heated to reflux. The dropwise addition of a solution of 92.6 g. (1.0 mole) of ¿er¿-butyl chloride® in 250 ml. of dry "unsaturate-free" n-pentane was then begun. After addition of about 5 ml. of the halide solution, the rate of reflux increased appreciably and the source of heat was removed. The remainder of the halide solution was then added over a 2.5-hr. period, at a rate such that sustained reflux was maintained throughout the addition. The reaction mixture was stirred for 0.5 hr. longer. The product solution was then filtered away from the residue of lithium chloride and excess metal through a sintered glass filter tube,7 89 1into a graduated dropping funnel (total volume, 589 ml.). Threemilliliter aliquots of the clear solution were then taken, hydrolyzed in flasks containing 10 ml. of standard 0.5AT acid, and back-titrated with standard O.liV base to a phenolphthalein end point. The yield of ¿er¿-butyllithium (based on ¿er¿-butyl chloride) was 89%.