October 7, 1910] 



SCIENCE 



481 



number and complexity of the factors involved in 

 chemical operations are so great that many opera- 

 tions are still carried on under the rule of thumb 

 guidance and have not been reduced to a science. 

 On the other hand, the trained scientific man is 

 very prone to believe that the matter with which 

 he deals will follow the laws which he has learned, 

 and for this reason he often overloolcs valuable 

 facts which the untrained observer sees. The 

 untrained observer ignores laws and systems, 

 tries any suggestion that comes along, and while 

 much valuable time and labor may be lost, the 

 loss is fully compensated by a few valuable suc- 

 cesses. The investigator who is successful follows 

 a mean between these paths. A number of prac- 

 tical illustrations of these principles were given. 



Factors Affecting the Electrolytic Method for the 

 Determination of Copper in Ores: W. C. Bas- 

 DALE and W. H. Cbeuss. 



The paper discusses and gives the results of 

 experimental data relating to the rate of precipi- 

 tation of copper, as affected by the form of elec- 

 trodes used, the amperage, the concentration of 

 the solution and the kind and nature of the acid 

 present. It is also shown that the presence of 

 salts of ferric iron merely delays precipitation 

 where no NO3 ions are present, but where the lat- 

 ter are present and the amount of iron is large, 

 complete precipitation is sometimes impossible. 

 This is attributed to the' formation of nitrous 

 acid, which has a strong solvent action on metallic 

 copper. The difficulty can be avoided by the addi- 

 tion of urea to the solution. 



The Electrolytic Determination of Zinc in Ores: 



Geo. Kemmeree. 



Recent workers obtained high results using an 

 electrolyte containing a small excess of sodium 

 hydroxide. These results were confirmed with 

 similar electrolytes. With 20 to 25 grams of 

 sodium hydroxide per 100 c.c. the results were 

 not high and all the zinc was precipitated. A 

 nickel gauze cathode and rotating anode were 

 used with a current N.D.io, 3.1 amperes. 



When applied to ores the sulphide obtained by 

 the "modified Waring" method contained iron. 

 This was eliminated by adding four to five drops 

 of concentrated hydrochloric acid to the neutral 

 solution where the Waring method calls for sis 

 drops of one-to-six acid. 



This sulphide dissolved in hydrochloric acid, 

 evap'brated with 2 c.c. of sulphuric acid to dense 

 fumes was dissolved in 100 c.c. of water, 25 grams 

 of sodium hydroxide added and electrolyzed. The 



results varied less than 0.3 per cent, and agree 

 well with the volumetric results on standard ores. 



The titles of other papers presented are as 

 follows : 

 Hcum or Efflorescence on Brick: A. F. Gbea'S'ES- 



Walkeb. 

 The Composition of Solids Precipitated from the 



Atmosphere during a "Salt Storm": W. C. 



Ebaugh. 

 The Scientific Use of Crude Petroleum as a 



Source of Power: Leon Labonde. 

 The Cuian Hedge Cactus; a Proposed Source of 



Crude Rubber: Chas. P. Fox. 

 Ficus elastica in Florida: Chas. P. Fox. 

 Some Recent Advances in Textile Chemistry: 



J. M. Matthews. 

 Alloys of Nickel and Cobalt with the Metals of 



the Chromium Oroup: Elwood Haynes. 

 Rust as an Accelerator in the Corrosion of Iron 



and Steel: W. D. Richaedson. 

 Rapid Estimation of Available Calcium Oxide in 



Lime Used in Cyanide Work: L. W. Bahney. 



DIVISION OF PHYSICAL AND INORGANIC CHEMISTRY 



Stratification in Suspensions: F. K. Cameron and 



E. E. Free. 



When a little very fine clay or similar material 

 is added to water and allowed to settle, there are 

 usually formed a number of strata differing in 

 clay content and which are separated by more or 

 less sharp surfaces. These surfaces move slowly 

 downward with the settling of the material. 

 Previous work on this phenomenon is largely 

 worthless because of the disturbing effects of 

 convection currents in the medium. The authors 

 have constructed a double-walled cabinet inside 

 which temperature changes are very slow and 

 uniform and by the use of which these convection 

 currents can be almost entirely avoided. Using 

 this cabinet, the rates of fall of the strata of a 

 number of clay-water mixtures have been care- 

 fully measured. The rate of fall of each stratum 

 is constant, but a stratum may divide into two, 

 one of which falls faster, the other more slowly, 

 than the original. This division may be several 

 times repeated. The number of strata formed in 

 any particular system and their rates of fall seem 

 to be determined partly by the nature of the 

 system and partly by other, and apparently acci- 

 dental, factors which are not yet understood. 



The Consolidation of Kaolin Precipitates: F. K. 

 Cameron and E. E. Free. 

 When mixtures of powdered kaolin with from 



