49-4 Scientific Intelligence. 



50" the piston sank through the mass without resistance. On 

 repeating the first experiment using a lever press, the piston sank 

 l*25 mm in an hour; a rate which would require 110 hours to 

 decompose the entire mass. Under the same conditions, potas- 

 sium sulphate gave no perceptible diminution of volume. Since 

 the chemical change is a function of the time, the acetate being 

 decomposed more rapidly the higher the temperature and press- 

 ure, it is evident that the molecules of a substance do not assume 

 the arrangement which corresponds to the given volume the 

 moment it is reached. Moreover, a substance can be compressed 

 without altering its state if the pressure does not last too long. — 

 Zeitschr. Physikal. Ghem.,i, 227-230; J. Ghem. Soc, liv, Abstr. 

 341, April, 1888. G. E. b. 



3. On the Vapor-density of Ferric Ghloride. — Geunewald and 

 Victor Meter have made a series of careful determinations of 

 the vapor-density of ferric chloride at various temperatures, with 

 a view of fixing its molecular formula. The chloride was pre- 

 pared by passing dry chlorine gas over fine iron wire, and after 

 sublimation, appeared as hexagonal plates, of a cantharides-green 

 color by reflected, and purplish red by transmitted light. For 

 the vapor-density in sulphur-vapor, 448°, the apparatus of Victor 

 Meyer was used, filled with nitrogen, the bulb of which was only 

 45 mm in diameter and 125 ram long, while the whole apparatus was 

 670 mm long. The boiling sulphur was contained in an iron tube 

 60 mm in diameter, and 620 mm long, heated in an air bath by six 

 Bunsen burners. As a mean of four accordant experiments, the 

 vapor-density at 448° was found to be 10-487. The chloride 

 after the experiments was carefully tested and found to contain 

 no trace of ferrous chloride. It therefore appears that even at 

 the temperature of boiling sulphur, the density of ferric chloride 

 is lower than 11% the value required by the formula Fe 2 Cl 6 . 

 The determinations were then repeated in the vapor of boiling- 

 phosphorus pentasulphide, 518°, in that of stannous chloride 606°, 

 and in Perrot's furnace at about 750°, 1050° and 1300°. The 

 mean vapor densities of ferric chloride at these temperatures were 

 found to be 9-569 at 518°, 8-383 at 606°, 5*459 and 750°, 5*307 at 

 1077°, and 5*135 at 1320°. It was found however that a pro- 

 gressive decomposition took place at these temperatures, about a 

 tenth of the chloride being decomposed at 518°, an eighth at 606° 

 and a third at 750° and above. The authors conclude that since 

 at 448° the vapor density of feri'ic chloride is less than corres- 

 ponds to the formula Fe 2 Cl 6 , and since experiments at lower tem- 

 peratures are not feasible, it follows that no temperature exists 

 at which ferric chloride has a density corresponding toFe 2 Cl 6 ; 

 and consequently since the vapor-density is lower, it must corres- 

 pond to the formula FeCl 3 . In order if possible to check the dis- 

 sociation of ferric chloride into ferrous chloride and chlorine, the 

 experiments were repeated in an atmosphere of chlorine ; the 

 vapor-densities obtained, however, were nearly the same as those 

 obtained in nitrogen. These results agree with those obtained for 



