1474 JOHN L. SPEIER, BF DAUBERT AND RR MCGREGOR Vol. 71 ... 3, 7, 11. Thymine was prepared by Dr. Marian Van Ess of the Golden State Co., and was measured in a 0.00019p M solution at PH 3, 7, 11. 5-Amino- and 5-nitrouracil (Eastman) were purified by repeated precipitation from aqueous solution and were measured in 0.000238 M and 0.000112 M solutions, respectively, at PH 3, 7, 11. Isobarbituric acid was obtained from Dr. FF Hey- roth af the ...