The primary dataset of 31 chemicals for DNA denaturation was tested by. The following DNA types have been tested: 53 T4 Bacteriophage, Diplococcus pneumoniae, B.subtilis, calf thymus, S. coli B, Serratia marcescens, Ps. aeruginosa and S. viridochromogenes. The majority of the experiments were done on the T4 Bacteriophage DNA at a concentration of 16µg/ml in a buffer containing 0.005 M Tris, and 10 -3 M EDTA, pH 7.6, and incubated for 30 minutes at 73 • C. Then DNA samples were cooled rapidly on ice. Following DNA denaturation, an immunologic method was used to identify solely denatured DNA. The logarithmic plot of the ratio of denatured to native DNA against the concentration of denaturing agents was used to calculate the concentrations of denaturing agents needed to give 50% denaturation of DNA under these conditions. The thermal DNA denaturation has also been studied using immunological and optical (refractometry, relative absorbancy of 260mµ)