The protonic acid content of some acid-type solid catalysts was determined by base exchange with 0.1 N ammonium acetate solution followed by pH measurement. This procedure also permitted evaluation of the relative acid strengths of the catalysts. Measurements were made on silica-alumina catalysts of various compositions after heat treatments ranging from 100 to 900°and were compared with data from non-aqueous butylamine titrations and propylene polymerization tests. Polymerization activity correlated better with protonic acid content than with total acids determined by butylamine titration for the entire composition range from pure silica to pure alumina. The results are consistent with the view that protons on the catalyst surface are necessary for acid catalysis such as heat treatment at 900°was regained by rehydration.
The m ethods investigated for the control of grain size in magnesium casting alloys were (1) stirring of carbonaceous solids into the molten alloy, (2) bubbling of carbon monoxide through the melt, (3) melting in a silicon carbide crucible, and (4) treatment wit h lump magnesite. In the last method, the magnesite was placed deep in the molten metal, where it dissociated thermally, generating a carbonaceous gas that bubbled through the m elt. The grain size and tensile properties were det ermined on sp ecimens from each melt, and these were compared with data from melts that had been superheated as we ll as those that had received no special treatment. Th e results indicate that magnesium alloys that have been properly treated with carbonaceous materials possessed grain-size and tensile properties eq uivalent to those obtain ed in s uperheated metal. The magne ite method is a simple, inexpensive, and convenient means of developin g a fine-grained structure in magnesium casting alloys.
Determinations of hydrogen in a variety of ferrous materials were made by vacuum extraction at 800 0 C and by vacuum fu sion. The warm extraction method has the advantages of rapid operation and relative freedom of the evolved hydrogen from association with other gases. A high hydrogen content produced by h eating in hydrogen at high temperature, or by electrolysis, is unstable at room temperature, but t he hyd rogen contents of commercial steels, after hot working and storage, were low and stable, and without segregation . Steels with high chromium contents dissolve more hydrogen and retain it more tenaciously than do plain carbon or low-alloy steels.
A modified hy drogen-reduction method yielded accurate values for the t otal oxygen content of several plain ca rbon steels, including steels that contained small amounts of alumina and silica, but yielded low results when larger amounts of alumina were present. The method was not applicable to the det ermination of the oxygen conte nt of open-hearth iron because of inability to separa te surface and body oxygen in this m aterial.
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