74 



SCIENCE 



[N. S. Vol. XLVII. No. 1203 



various stages of treatment. It was shown that 

 while considerable variation in resistance could be 

 produced by annealing, this variation was not ac- 

 companied by structural changes of a nature that 

 could be easily detected under the microscope. 



Thermophysics of sine and its alloys: J. W. 

 Richards. The author discusses some physical, 

 particularly thermal, data which are lacking with 

 respect to zinc and its chief alloys, Ijrass and 

 bronze, and calls attention to the great need of 

 laboratory work to determine these constants. 

 The data needed, such as vapor tensions at low 

 temperatures, and latent heat of evaporation, are 

 constants of nature, difOlcult to determine, yet of 

 primary importance to the zinc industry if accu- 

 rately determined and properly and intelligently 

 used. 



Recent developments in connection with the use 

 of sulphur dioxide in hydrometallurgy : Edward 

 E. Weidlein. The process developed by the au- 

 thor is based upon the precipitation of copper by 

 means of sxilphur dioxide. In precipitation, the 

 solution is neutralized vpith lime and treated vrith 

 sulphur dioxide until it has dissolved a percent- 

 age of gas equal to that of the contained copper. 

 The precipitation of metallic copper ensues in- 

 stantly when the solution is brought to a tempera- 

 ture of 160° C. under a pressure of 100 pounds. 

 The mechanical arrangements are such that the 

 processes of dissolution and precipitation are con- 

 tinuous. The copper assays, when melted, over 99 

 per cent, pure and contains oxygen as the sole 

 impurity. 



The importance of the flotation process in the 

 metallurgy of copper: B. P. Mathewson. Proc- 

 ess revolutionary : There is more ore handled daily 

 by flotation than by any other non-ferrous metal- 

 lurgical process. Prior to adoption of process the 

 concentration losses were seldom less than 20 per 

 cent.; now they are seldom over 8 per cent. Sav- 

 ings now so great that the so-called hold-up by 

 owners of patents can not cripple the users of the 

 process. Process is a rule of thumb development : 

 The theory is now being worked out, but no 

 whoUy satisfactory theory has yet been evolved. 

 Canadian users can afford to take chances on out- 

 come of litigation, as they will only be compelled 

 to pay reasonable royalties. 



The theory of froth: Wilder D. Bancroft. 

 Froth is a closely packed mass of bubbles having 

 a cellular or honeycomb structure, the walls of the 



cells being liquid films. Froths are more stable, 

 the more viscous the films; and the films can be 

 made more viscous by adding solids. 



Chemicals used in ore flotation: Olfvee C. Bals- 

 TON and L. D. Yundt. The use of certain chemicals 

 in the flotation concentration of ores has been de- 

 scribed and theories of the action of these chem- 

 icals have been explained. The use of chemical 

 addition agents in ore-pulps during flotation is 

 only in its infancy, and as the process is better 

 understood operators will make greater use of 

 chemical addition agents which will allow them 

 to obtain the highest economic results. The 

 possibilities of such applications are almost un- 

 limited and it is probably along lines of this 

 kind that some of the great advances in ore flota- 

 tion will be made. 



The selective action of cadmium salts on lead 

 and zinc sulphides in flotation : M. H. Thornbeket. 

 The experiments so far completed show that the 

 presence of cadmium salts practically stops lead 

 sulphides from floating. The effect of these salts 

 on zinc sulphides will be carried out in time to 

 give results in the final paper. 



Flotation experiments on zinc sulphide tailings, 

 III.: "W. A. Whitaker, S. F. Farley and H. P. 

 Evans, (a) The Effect of Certain Mixtures of 

 Oils. — ^A previous series of flotation tests carried 

 out in this laboratory on a zinc sulphide tailing 

 showed that the lighter wood distUlates and cer- 

 tain vegetable oils displayed good selection for 

 the mineral and yielded rich concentrates, while 

 coal and wood tar mediums did not show such se- 

 lection between mineral and gangue, but yielded 

 high extractions. A series of tests was made in 

 order to learn the effect of mixing a good "con- 

 centrating" medium with a good extracting 

 medium, and of mixing certain lighter oils, (b) 

 The Effect of Organic Solvents. — Solvents such as 

 benzol, alcohol, kerosene, turpentine and gasoline 

 were used with different oils in order to deter- 

 mine whether this method of emulsifioation would 

 exert a favorable effect in flotation. The method 

 was carried out under neutral, acid and alkaline 

 conditions on tailings from the Joplin District, 

 (c) A Comparison between the "Mechanically 

 Agitated" and "Pneumatic" Types of Flotation 

 Machines. — Several tests mentioned under (a) 

 and (6) were made in machines of both types. 

 The resxilts obtained, as regards richness of con- 

 centrate and percentage extraction, were compared 

 and plotted. 



