426 Scientific Intelligence. 



atskt has considered it desirable to test the question whether in 

 the case of slow reactions, the speed is influenced by the passage 

 of the medium into the serai-solid state, like a jelly. For this 

 purpose he selected the katalysis of methyl acetate by hydro- 

 chloric acid. Two solutions were prepared : one containing 20 

 c. c. half-normal hydrochloric acid, with 10 c. c. of water and one 

 c. c. methyl acetate; the other 20 c. c. of the same acid, with 10 

 c. c. agar-agar solution of 1'25 per cent, and 1 c. c. methyl 

 acetate. These solutions were placed in separate vessels and the 

 temperature regulated by a thermostat to 25°. The strength of 

 the agar-agar solution was so regulated, that at 35° the mixture 

 was completely liquid, while at 25° it was so solid that the vessel 

 could be inverted without showing more than traces of flowing. 

 At the same time, the jelly had so little coherence that it could 

 be drawn into a pipette with a somewhat large opening and could 

 be so far divided by stirring with a glass rod as to permit of 

 titration. Two parallel sets of experiments were made, the c. c. 

 of baryta water required to neutralize the acid in one c. c. of the 

 solution being noted at equal intervals for each solution. The 

 numbers given in the paper show that in both cases the speed of 

 the reaction is the same, within the errors of experiment. This 

 result indeed might have been expected. The speed of chemical 

 changes in homogeneous systems depends not on the greater or 

 less speed of the final masses with regard to each other, but upon 

 that of the molecular motion ; so that it is a function not of the 

 interior friction, but of the diffusion-coefficient. Since therefore 

 it has been proved that the speed of diffusion in agar-jelly is the 

 same as in pure water, it follows that the speed of chemical 

 change cannot be materially altered by the presence of the jelly. 

 Still it was important to establish this result by direct experi- 

 ment. — Zeitschr. physical. Chem. 9 vii, 34, Jan., 1891. g. f. b. 



2. On the Direct-reading of Volumes in Vapor-density Deter- 

 minations. — Luxge and Xeubeeg have applied the apparatus, 

 contrived by the former chemist for the direct reading of gas 

 volumes,* to the determination of vapor-densities. For this pur- 

 pose they attach the Meyer bulb to the measuring tube in place 

 of the gas evolution flask. After the vapor in the bulb has ex- 

 pelled the corresponding volume of air, the pressure tube is 

 raised until the level of the mercury in the reduction tube reaches 

 the normal mark. Since under these conditions the gas-volume 

 is also at the normal pressure and temperature, this volume may 

 be directly read off. If this reading is in cubic centimeters, g 

 grams of the substance give v cubic centimeters of vapor, and 

 the density D=g/u. 0-001293. By this method the vapor density 

 of benzene was determined as 2*66 — 2*76, that of naphthalene 4*2, 

 that of triphenyl-methane 8*24, and that of mercury 6*8. In all 

 these cases except the first, the temperature of determination was 

 below the boiling point of the substance; the value of mercury 

 for example being obtained in the vapor of diphenyl at 254°, the 



*Tkis Journal. III. xxxix, 396, May, 1890. 



