September 1, 1916] 



SCIENCE 



325 



successive reagents being zine salts, silver salts, 

 mercuric salts, alkaline formates, metallic copper 

 and cuprous salts. 



On Some Molecular Compounds in Glass: E. W. 

 Tillotson. 



On the Variable Rotatory Power of Dissolved Or- 

 ganic Substances: M. A. Eosanoff and H. A. 



- Morton. 



On the Constant a of Van der Waal's Equation: 



M. A. EOSANOFF AND H. C. CORLISS. 



On the Change of Transition Points with Pressure: 

 M. A. Eosanoff. 



A national Process of Fractional Distillation: M. 

 A. Eosanoff. 



A Study of Some of the Physical Properties of 

 Mixtures of Dielectric Oils and Water. (Pre- 

 liminary Report.) : L. I. Shaw and L. A. Pap- 

 penhagen. 



Change of Conductivity with Time in the System 

 MeOH + I 2 . (Preliminary Report.) : L. I. Shaw 

 and J. P. Tricket. 



Atomic Weight of Yttrium: C. W. Balke and B. 

 S. Hopkins. 



The Potassium Iodide Reaction for Platinum: W. 



J. Prince and H. C. P. Weber. 



The cherry-red, to rose, tint which is produced 

 in platinum solutions by means of potassium iodide 

 is one of the most sensitive tests known. Appar- 

 ently well-suited for the purpose of colorimetric 

 estimation of the quantity of platinum in solu- 

 tions, the reaction has not been used for this pur- 

 pose for lack of ability to properly control condi- 

 tions. 



This investigation shows that the resulting color 

 is not the result of the formation of a reduction 

 product, such as a platinous compound or of col- 

 loidal platinum. There is an intermediate forma- 

 tion of a complex iodide, and the water plays an 

 essential part (hydrolysis) in the reaction since 

 the color is not developed in certain other solvents. 

 Immediately after development of maximum color 

 intensity has been attained a colloidal phase can 

 be distinguished in the ultramicroseope, but this is 

 platinum iodide. The rate of the reaction is af- 

 fected enormously by the quantity of KI present. 

 If only theoretical proportions of this substance 

 are added (6KI: 1 Pt) the reaction goes almost 

 directly to black colloidal Ptl t . The reaction 

 curves show that 4 to 5 times the theoretical quan- 

 tities of KI are necessary to produce satisfactory 

 results. As little as 2 X 10~'g. Pt may be recog- 

 nized in 1 c.c. of solution. 



Prom consideration of the optimum conditions 

 necessary for the production of the desired color 



reaction it is hoped that a colorimetric method for 

 the estimation of Pt may be developed. 



The Viscosity of Alcoholic Solutions: O. F. Tower. 

 The Relation between Molecular Cohesion and Sur- 

 face Tension. Ebtvos Law : Albert P. Mathews. 

 Determination of Aluminium as Oxide: William 

 Blum. 



The various factors affecting the precipitation, 

 washing and ignition of aluminium hydroxide in 

 quantitative analysis were studied. By means of 

 the hydrogen electrode it was found that the pre- 

 cipitation is complete at a point between the turn- 

 ing points of the indicators methyl red and rosolie 

 acid, the use of which is therefore recommended. 

 The conditions for the accurate estimation of 

 aluminium are defined. 



A Study of Tantalum Pentachloride for Atomic 



Weight Purposes: G. W. Sears and C. W. 



Balke. 

 A Study of the Dialysis of a Colloidal Solution of 



Hydrous Chromic Oxide in Chromium Chloride: 



Marks Nedjle and J. Barab. 

 The Temperature Effect in Dialysis, and a Simple 



Rapid Dialyzer: Marks Needle. 

 Production of Triatomic Hydrogen by Radium 



Rays: G. L. Wendt. 

 The Effect of Dissolved Substances on the Velocity 



of Crystallization of Water: J. H. Walton and 



A. Braun. (Lantern.) 



The Atomic Weight of Dysprosium: C. W. Balke 



and E. W. Engle. 



Dysprosium material was purified by the alkali 

 sulfate separation, followed by fractional crystalli- 

 zation of the bromates, ethylsulfates and nitrates. 

 For the atomic weight determinations the oxide- 

 chloride ratio was studied. Dysprosium oxide, 

 Dy«0 3 , was placed in a tarred quartz flask, weighed, 

 dissolved in HC1, and the chloride dehydrated, 

 fused and weighed in the flask. Five consecutive 

 determinations gave the values 164.354, 164.357, 

 164.116, 164.104, 164.207. Mean value 164.228. 

 This is considerably higher than the value now in 

 the International Table. 



Potassium Lead Tartrate: E. S. Dean. 

 The Density of Aqueous Copper Sulphate-Sul- 

 phuric Acid Solutions: H. D. Hollee and E. L. 

 Peffer. 



The densities of solutions of copper sulphate 

 and sulphuric acid varying in concentration from 

 to 20 per cent, of each solute, were determined 

 at 25° and 40° C. The densities were found to be 

 approximately additive, and to be dependent upon 

 the total concentration of the two solutes. 



