224 Chemistry and Physics. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On a Vapor-calorimeter. — Bttnsen has described a new 

 calorimeter based on the principle, first employed by Joly, of 

 using the condensation of saturated water-vapor of constant tem- 

 perature as the calorimetric measure. Having carefully studied 

 the problem, the aitthor has confirmed the practicability of the 

 method, and has constructed an instrument in which the principal 

 difficulties are entirely overcome. The body whose specific heat 

 is desired is placed in a platinum basket and suspended in the 

 vapor of boiling water. The water which is condensed during 

 the heating of the body, is retained in the basket and can be 

 weighed provided the weighing is done in the vapor. From the 

 weight thus obtained, since the latent heat of condensation of 

 water-vapor is known, the amount of heat absorbed by the body 

 in raising its temperature through the given number of degrees 

 may be calculated. — Ann. Phys. Chem. II, xxxi, 1 ; Per. Perl. 

 Chem. Ges., xx, 275 (Ref.), May, 1887. g. f. b. 



2. On the density of liquid Methane, Oxygen and Nitrogen. — 

 By the use of his apparatus, Olszewsky has been able to obtain 

 13 to 15 c.c. of any desired gas in the liquid condition, cooled by 

 boiling ethylene and liquefied by pressure. The liquid is col- 

 lected in a double glass tube, and when freed from external pres- 

 sure, the exterior layer evaporates first under the influence of the 

 relatively warmer ethylene, while about 4 or 5 c.c. of the sub- 

 stance remains in the inner tube cooled in this way to its own 

 boiling point. This portion of liquid is thoroughly protected 

 against the access of heat, and can evaporate therefore only with 

 proportionate slowness. At a given moment its volume may be 

 read off on a scale engraved on the glass tube in which it is con- 

 tained. Its mass may easily be determined from the amount of 

 gas given by its evaporation ; and from these data the density of 

 the liquid is readily calculated. The densities of methane, of 

 oxygen, and of nitrogen thus found are as follows, at the tem- 

 perature of their boiling points : 



Density. 



Methane, 0-415 



Oxygen, 1-124 



Nitrogen, 0-885 



— Ann. Phys. Chem. II, xxxi, 58 ; Per. Perl. 

 (Ref.), May, 1887. 



3. On the experimental demonstration of Avogadro's Hypothe- 

 sis. — Schall has constructed a balance so that the ratio of the den- 

 sity of any given gas to that of hydrogen — and hence the molec- 

 ular weight of this gas — -may be read directly from the deflection. 

 Two glass globes are provided, the capacities of which are as 

 nearly equal as possible, and whose weights are equalized by 

 means of a suitable counterpoise. The balance carries a combined 



Boiling point. 







— 164-0° 







— 181-4° 







— 194-4° ' 







Chem. Ges., 



XX, 



,276 



G. 



F. 



B. 



