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A seri es of selected or specially prepared catalysts were s tud ied fo r t heir abili ty to accelerate the ortho to para conversion of hydrogen . The res ults of t hi s st ud y a re presented and the p erformance of vari ous catalyst s are compared with t hat of chrom ic oxide on al u: mina pellets. An outstandin g cata.lyst, u~s upporte d hydrous J erric oxide g ra nules, was selected for further study a nd used 111 the liquefi ers of t he NatIOnal Burea u of Standards Cr yogenic Engineering L aboratory. One and one-half liters of t his catalyst has now bee n used to convert more t han 100,000 li ters of liquid hydrogen to 90 to 95 perce nt pa ra at an average rate of abo ut 235 liters of liquid per hour. There is to date no ev id ence of decrea se in effici ency with continued use.
Weitzel et al. (Sat,) studied this question.