November 14, 1913] 



SCIENCE 



711 



with oxygen. This complex is unstable and decom- 

 poses by rise of temperature so as to form water, 

 COa and CO. Below 200° C. water is the principal 

 product of the oxidation of coal. Carbon dioxide 

 and carbon monoxide are formed in increasing 

 amounts at 110° C. and above, by decomposition of 

 the intermediate complex. 



The bearing of the results on deterioration and 

 spontaneous combustion, inflammability of coal 

 dust, methods of analysis of coal, and problems of 

 mine ventilation and mine fires is brought out. 



DIVISION or PHYSICAL AND INORGANIC CHEMISTRY 



S. L. Bigelow, Chairman 



E. C. Wells, Secretary 



B. C. Wells: Otservations on the Electrochemical 



Behavior of Minerals. 



It has been found that pyrite, which ia a com- 

 mon constituent of most ore deposits, is capable of 

 functioning to some extent as an unattackable 

 electrode, so that chemical differences between solu- 

 tions in ore deposits may be equalized through 

 electrical action over appreciable distances as well 

 as by direct mingling of the solutions. Such action 

 would, however, require some sort of a liquid circuit 

 in addition to the conducting mineral. A solution 

 of sodium sulphide in contact with pyrite consti- 

 tutes an anode combination of sufficient power to 

 precipitate gold, silver, mercury and copper from 

 their soluble salts upon a cathode of pyrite in an 

 arrangement like a "chemometer. " In fact, 

 pyrrhotite and chaloocite in water alone suffice as 

 anodes for the same purpose. The action of the 

 more attackable minerals is due principally to their 

 own solution-products so that the additional effects 

 possible with unattackable electrodes are less 

 marked. 

 Eugene C. BiV!GSi.M: Fliddity and van derWaals's 



Equation. 



Batschinski3 has proved that the fluidity 4> of an 

 unassociated liquid is a linear function of its 

 volume (d) only, up to the critical temperature, 

 i. e., i; = tt) + c0, where w is a constant which is 

 the sum of the atomic constants, and c is a con- 

 stant which may be calculated. Substituting this 

 value into the equation of van der Waals we obtain 

 a relation between the fluidity of a liquid and the 

 temperature and pressure 



pk 



+ 4(«-6)- 



a/Rc 



ab 



and all of these constants may be obtained without 

 3 Ann. Soc. d 'encourag. sciences exper., Supple- 

 ment, 3, 1913. 



further viscosity measurements. Hence it is theo- 

 retically possible to calculate the fluidity of any 

 non-associated liquid as soon as its expansion 

 coefficients are sufficiently well known. 



It can be shown that the above formula works 

 out admirably in practise. Since in ordinary viscos- 

 ity measurements, the pressure is constant and the 

 last term of the equation may be neglected, we have 



2' = ^*+^-^' 

 where A, B, C and D are constants. An equation 

 of this form will reproduce* the observed fluidities 

 of the 85 substances measured by Thorpe and 

 Rodger with a mean deviation for no substance 

 equal to 0.1 per cent. In fact for most substances 

 2) may be made equal to zero, and satisfactory 

 results obtained with the simple formula 

 T = A4> + C — B/<t>. 



The measurements of Phillips!- confirm the view 

 that the 0, p, T curves are similar to the familiar 

 V, p, T curves up to the critical temperature. 

 Beyond the critical temperature does not increase 

 as the pressure is lowered, as is true of the volume. 

 This leads to interesting and hitherto unnoticed 

 relations between "collisional" and " diffusional " 

 viscosity. 

 E. C. McKelvy and F. A. Wertz: The Solubility 



of Water in Hydrocarions. 



The critical solution temperature in certain 

 systems of two liquids varies greatly with small 

 additions of moisture. Solubility curves were 

 determined for the systems methyl alcohol-turpen- 

 tine, methyl alcohol-ligroin and ethyl alcohol- 

 kerosene, with the dry hydrocarbons. The curves 

 showing the variation of the maximum with small 

 additions of water were then plotted. The hydro- 

 carbons being saturated with water at any given 

 temperature, the critical solution temperature found 

 gives from these curves the amount of water dis- 

 solved in the oil. Calcium chloride was found to 

 be most effective in drying the oils without other- 

 wise changing their composition. 

 L. M. Dennis and B. J. Lemon: Electrolysis of 



Solutions of the Rare Earths. (Lantern.) 

 Wilder D. Bancroft: Action of Light on Copper 



Sulphate Solution. 

 Wilder D. Bancroft: Catalysis of Acetic Acid. 

 E. C. McKelvy: The Critical Solution Tempera^ 



ture and Its Use in the Estimation of Moisture. 



The variation of the critical solution temperature 

 of two liquids on the addition of a third com- 



^Zeitschr. f. phys. chem., 66, 238 (1909). 



'sProc. Boy. Soc. London, 87A, 56 (1912). 



