408 Serentific Intelligence. 
According to Avogadro’s law equal volumes of different gases 
under the same pressure and temperature contain the same num- 
ix of molecules, the ratio of the sum of the sections is the are of 
the section of the molecules themselves. Bearing this in mind, one 
is justified, since the mean accuracy of the numbers found ean be 
depended upon within eight per cent, in regarding, in the follow- 
ing tables, the numbers found for the two-atom molec ules, with 
the exception of chlorine, hydrogen and hydrochlorine, as ‘equal 
among themselves, and the section of t e hydrogen sist ean as 
one-half and that of Sorel as twice as great. The three-atom 
molecules of CQ,, N,O, of H,O and of H,S have the same 
molecular sections mae stand in relation to the large number of 
two-atom gases as 3:2 or as the number of atoms. To this law 
SO, is an exception, since its molecular section is the same as that 
of chlorine. H,N and HCl take a decided position. Possibly 
, can be eee pe with them, since the mean of nage three 
numbers is related to the molecular section of the two-atom 
molecule nearly as 4:3. One is also tempted to regard the molec- 
ular sections of C,H,, of SO,, of haaiaee and CH,Cl as equal and 
as double that of the two-atom molecule. 
e following table includes the sum of the molecular sections 
of each gas in a cubic centimeter, expressed in square centimeters 
9100 approximately 9000 =1 X 9000 
90 = 18000 
» 16900 0 
N 18000 . 18000 
Two-atom cd 18200 MS 18000 f = 2 X 2000 
N 18700 eg 18000 
wa 26700 . 27000 
r N 26800 " 27000 
Three-ntom + sy ohaon . grove f2 7  " 
H,S 28600 u 27000 J 
CH, 21600 = 2400 
H,N 23400 ss 24000 } = § x 9000 
HCl 24200 . 24 
C,H, 31600 at 36000 
SO, 36700 * 36000 
"3670 “ ee Eeaeee ared Nis 
CH,Cl 39300 “ 36000 
Professor Riihlmann also gives the following values of p. 
For nitrogen molecule = 34°10-® cm. 
For carbonic dioxide molecule = 16°107® em, 
For hydrogen molecule == 41°10-* om. 
At 0° and 760 mm. pressure a cubic centimeter holds nearly 
100 trillions of gas molecules. Under these conditions the mole- 
cules themselves fill nearly the three-thousandth part of the space 
occupied by the gas. The absolute weight of a hydrogen mole- 
cule is represented by 15-107? f and the specific weight as 360.— 
Beiblitier Annalen der Physik und Chemie, 1879, No. 2, th 57. 
