Chemistry and Phys^cs. 313 



has applied Lorentz's theory of electrical ions to the Hall phe- 

 nomenon and has obtained an equation which represents the elec- 

 tromotive force obtained by Hall. He concludes that it would be 

 desirable to examine whether all metals exhibit the Hall effect 

 when they carry currents of very high electromotive force and 

 whether a change of sign occurs. — Gomptes JZendus, No. 6, Feb., 

 1899, pp. 339-341. j. t. 



12. On the Relation of the Surface Tension and Specific Gravity 

 of certain Aqueous Solutions to their State of Ionization. — Prof. 

 MacGregor has shown that it is possible to calculate the various 

 properties of solutions of potassium and sodium chloride in terms 

 of the state of ionization of the electrolytes contained. The rela- 

 tion derived, in its simplest form, is S=S w -{-k(l — a) n + l a ?i . 

 where S is the numerical value of any property of a solution 

 (density, surface tension, etc.), S w that of the same property of 

 water under the same physical conditions, n the number of equiva- 

 lent gram-molecules per unit volume, a the ionization coefficient 

 of the electrolyte in the solution, and I and k constants, called 

 ionization constants, for any given property of any given electro- 

 lyte. Mr. E. H. Aechbald has carried out a similar series of 

 observations and calculations in the case of simple solutions of 

 sodium, potassium and copper sulphates, salts of more complex 

 molecular structure than those previously examined. He con- 

 cludes that the expression given represents observed values of the 

 surface tension and specific gravity of the solutions examined 

 through a range of concentration extending from 0*05 to about 0*4 

 or 0*5 equivalent gram-molecules per liter. Further, that it is pos- 

 sible by aid of the dissociation theory of electrolysis to predict 

 the surface tension and specific gravity of mixtures of potassium 

 and sodium sulphate solutions and the specific gravity of mixtures 

 of solutions of potassium and copper sulphates throughout nearly 

 the same range, within the limits of the error of observation. 

 And similarly, that it is possible to predict the specific gravity of 

 mixtures of solutions of potassium sulphate and sodium chloride. 



13. On the Gause of the Absence of Coloration in certain Lim- 

 pid Natural Waters. — Professor W. Spuing has an interesting 

 article upon this subject in a recent number of the Bibliotheque 

 Universelle (Jan. 15, 1899). Recognizing the accepted fact that 

 pure water is distinctly blue, he remarks that the green color 

 often observed is easily explained as due to the presence of more 

 or less muddiness, which acts with the natural blue color to give 

 a sensation of green. The absence of color, however, is a dif- 

 ferent problem, as early noted by Berzelius. The results of some 

 experiments have led the author to the hypothesis that the sus- 

 pension of minute, perhaps invisible, particles of anhydrous 

 ferric oxide, or hematite, would have, through their red color, the 

 effect of neutralizing the blue and leaving the water completely 

 colorless. He notes the fact that microscopic grains of hematite 

 are- almost always found distributed in the soil, and that terres- 

 trial waters have rarely the blue color which the pure liquid 



Am. Jour. Sci.— Fourth; Series, Yol. VII, No. 40.— April, 1899. 

 21 



