Chemistry and Physics. 825 



taining the positive electrode. The fact seems to be that the 

 positively charged copper ions, coming in contact with the film of 

 ferrocyanide through which they cannot pass, give up their 

 charges and are deposited in the metallic state ; the negative 

 FeCy 6 ions, accumulating on the other side of the film and there 

 giving up an equivalent of negative electricity, are converted 

 into triad ferrocyanide ions. At the other film the potassium 

 ions permeating the copper ferrocyanide film, pass through it and 

 establish electrical equilibrium by uniting with the S0 4 ions of 

 the copper sulphate. The author thus explains Becquerel's ob- 

 servation that when a tube containing copper nitrate solution is 

 placed in a solution of sodium sulphide, a deposit of copper takes 

 place in the interior of the tube. He also shows that many elec- 

 trophysiological phenomena may be explained in this way, by the 

 action of semi-permeable materials ; such for example as the 

 secondary resistance of albumin noticed some years ago by 

 Dubois Reymond. — Zeitschr. physikal. Chem., vi, 71; J. Chem. 

 Soc, lviii, 1354, Dec. 1890. G. f. b. 



5. On AMotropic Silver. — Prange has observed that after 

 preparing, according to the method described by Carey Lea, 

 the allotropic form of silver soluble in water, there remained 

 in the solution a colloidal form in the dissolved state. The 

 behavior of this solution, not only under the action of light but 

 also at increased temperatures, has been studied by him and he 

 finds that a separation of the dissolved silver takes place in both 

 cases. The maximum concentration of the solution observed by 

 the author was 4*75 grams per liter. In order to study the 

 properties of the second modification of silver described by Carey 

 Lea, the method of preparation was so modified as to permit of 

 larger quantities being obtained pure in a short time. Silver 

 nitrate solution was precipitated with ferrous sulphate and sodium 

 citrate, the liquid decanted from the precipitate and the latter 

 dissolved in water. On the addition of ammonium nitrate, the 

 silver separated and was washed with water containing some 

 ammonium nitrate. It was then filtered off, washed with alcohol 

 and dried over sulphuric acid ; all these operations being per- 

 formed in the dark. The silver so prepared is no longer soluble 

 in water. It is not entirely pure silver, though it contains no 

 Ag 4 since on ignition it does not give up oxygen. — Ber. Berl. 

 Chem. Ges., xxiv, (Ref.) 69, Feb., 1891. g. e. b. 



6. The Continuity of Solid and Liquid ; by Carl Barus 

 (communicated). — Suitably adapting Kopp's well-known specific 

 volume flask in such a way, that by means of a filament of zinc 

 sulphate solution, the reading can be made electrically, at any 

 temperature or pressure whatever, I obtained a method for the 

 full and precise study of the solid-liquid volume thermodynamics. 

 I am thus able to map out the isothermals and isopiestics, the 

 relation of melting point and pressure, the relation of specific 

 volumes at the melting point and pressure, together with some 

 description of the behavior of solid matter in a suite of operations. 



