摘要:

A study was made of the precipitation, by means of zinc dust, of copper and cadmium from a "normal thickener overflow" solution as obtained in the hydro-metallurgy of zinc. The effect of (i) the quantity of zinc dust added, (ii) the initial pH of the solution, (iii) the time of agitation, and (iv) the aeration of the solution were studied. The polarograph was used to follow the changes in the concentration of the solution.For the effective removal of cadmium, the initial pH of the solution should not be below 3.5. The time of treatment with zinc dust should be controlled within narrow limits and, while the agitation should be effective, it should not cause aeration of the solution. The redissolving of cadmium on prolonged treatment appears to be a typical process of electrolytic corrosion analogous to underwater corrosion of iron in the neutral zone, the rate of redissolving being dependent on the supply of oxygen for depolarization. Similar redissolving of copper does not take place under the conditions studied and, given sufficient zinc dust, only the minimum time of treatment need be controlled.

ISSN:1923-4287    

DOI:10.1139/cjr42b-016

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

A kinetic study has been made of the decomposition of benzoyl peroxide in benzene. Kinetic data for this study have been obtained from three separate sets of measurements. Rate measurements from evolved carbon dioxide and direct iodometric measurements of peroxide are in good agreement. Alkali-metric determinations of the product, benzoic acid, have also been made during the course of the reaction.Gravimetric determinations show that the total evolved carbon dioxide from the reaction is a function of the temperature, and indicate that the mechanism involves two parallel fast reactions, one of which evolves one mole of carbon dioxide per mole of peroxide and the other two moles of carbon dioxide per mole of peroxide. The latter reaction predominates at higher temperatures.A kinetic analysis is included and provides for a slow reaction involving the rupture of the peroxide bond, followed by free radical reactions.The secondary free radical reactions would probably form hydrogen radicals, but there is evidence to support the view that these hydrogen radicals are not eliminated by mutual termination.The reaction is first order and the energy of activation was found to be 31,000 cal. per mole.

ISSN:1923-4287    

DOI:10.1139/cjr42b-017

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

The amylase system of birch sap consists of a cellobiogenic amylase and most probably a glucogenic amylase. The optimum conditions of pH and temperature are pH 5. 5 at 4 °C. to 6.3 at 60 °C. The maximum production of cellobiose occurred at a temperature of 50 °C. at the optimum pH for this temperature. The optimum conditions for the production of glucose were pH 5.5 and a temperature of 50 °C.It is felt that these new facts throw some additional light on the constitution of starch, and that possibly birch sap might serve as a source of cellobiose, which has heretofore only been prepared commercially by hydrolysis of cellulose acetate.

ISSN:1923-4287    

DOI:10.1139/cjr42b-018

出版商:NRC Research Press    

年代:1942

数据来源: NRC