Oxidation of zinc vapor by carbon dioxide

NOTES

FROM THE DEPARTMENT OF THE INTERIOR, BUREAU OF MINES.*

OXIDATION

OF

ZINC

VAPOR

BY CARBON

DIOXIDE.

By B. M. O’Harra. BECAUSE of the important effect of carbon dioxide on the condensation of zinc vapor in the metallurgical treatment of zinc ores, experiments were made to determine the concentration of carbon dioxide necessary to oxidize zinc vapor at various temperatures. Although the preliminary experiments failed to give the quantitative information desired, they proved that the required concentration of carbon dioxide increased with rising temperature. It was found that zinc oxide was reduced at 750~ C. by carbon monoxide even when carbon dioxide was present in large proportions, but that partial reoxidation took place in the cooler part of the reaction tube. The weight of zinc oxide reduced in a given time decreased with increasing ratios of carbon dioxide, and when 90 per cent. of carbon dioxide was present, the reduction and reoxidation was manifest only by a transfer of zinc oxide from the hot to the cooler part of the tube. In the preliminary experiments with zinc, it was found that oxidation took place in the cooler parts of the reaction tube, even when the concentration of carbon dioxide was not enough to oxidize zinc in the hot part of the tube. It was furthermore found that all carbon dioxide was converted to carbon monoxide by reaction with zinc at some temperature between 750” C. and room temperature, if enough time were allowed for the completion of the reaction. r+?th the knowledge gained from these preliminary experiments a final series of experiments was planned, from which the desired quantitative data were obtained. These data were plotted and a curve drawn from which may be found the minimum concentration of carbon dioxide at any given temperature that will have an oxidizing effect on zinc vapor under the conditions of zinc condensation in metallurgical practice. It has also been demonstrated that the oxidation of zinc vapor by carbon monoxide is theoretically possible, though this oxidation

*Communicated

by the Director,

Bureau

of Mines. 421

422

U. S. BUREAU OF MINES NOTES.

[J. F. I.

is ordinarily of little practical importance. A fuller account of the experiments will be found in Technical Paper 336 of the bureau, which is now available. THE PURIFICATION

OF COPPER SULPHATE

SOLUTIONS.

By George S. Tilley and Oliver C. Ralston,

ONE of the main deterrents in the use of sulphuric acid leaching and electrolysis for extracting copper from its ores has been the fouling of the solutions with soluble impurities of the ore, especially iron and aluminum. Any simple, inexpensive means of removing these two impurities would be useful in leaching and refining copper, in purifying bluestone-plant solutions, and in treating mine water that contains copper. The writers, therefore, took up this problem. A study of previous work by various investigators showed that the removal of iron and aluminum, and incidentally arsenic, antimony, bismuth, and tin, from copper sulphate solutions, has been effected satisfactorily in a number of processes, but details were lacking on the best operating conditions, methods of controlling the reactions, or the basis of procedure. The writers then selected for further research an investigation of hydrolytic agents, as the most promising field of work. The limitations of cost, availability, and suitability to other conditions limited the tests chiefly to carbonates and oxides of copper and calcium. It was found that ferric iron and aluminum can be precipitated from copper solutions, and ferrous iron oxidized by aeration. The removal of ferrous iron was very slow, but the use of higher temperatures and fine-bubble aeration in an apparatus devised by Further tests on a commercial the writers gave better results. scale show that practically all of the iron can be removed, but as the reaction approaches completion, the rate of oxidation and removal becomes very slow. Further details will be found in Technical Paper 359, recently issued by the Bureau of Mines. THE

ELECTRICAL

MANUFACTURE OF CARBON By J. J. Jakosky.

BLACK.

EXISTING and proposed legislation against the present method of producing carbon black from natural gas and the continually increasing demand for the gas for other purposes, indicate that