A chromatographic column consisting of kieselguhr impregnated with methylated albumin, for fractionating nucleic acids by their molecular size, has been reported (Mandell & Hershey, 1960; Hershey & Burgi, 1960). A simplified form of the technique using stepwise elution revealed more properties of the column, such as recognition of base composition and of hydrogen bond content of DNA. It is found that DNA with greater guanine—cytosine content is eluted at lower salt concentration. Furthermore, thermally denatured DNA is eluted in higher salt concentration than is native DNA. Using this method, a naturally existing “deoxypolyadenme-thymine” in a marine crab (Cancer borealis) was isolated from the main DNA of the animal. The method has also been applied to fractionate RNA, and it was found that it not only separates soluble and ribosomal RNA (Mandell & Hershey, 1960), but also 16s and 23s ribosomal RNA.