154 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Molecular Masses of Gases. — It has been shown by 



D. Berthelot that in consequence of the difference between the 



coefficients of expansion and compressibility, the molecular masses 



of gases are proportional, not to the actual density, but to the 



product of this value into the molecular volume. The molecular 



P 

 volume of a gas is given by the formula v = v — [1 + a (p—p )] = 



p . . P° 



v — (l+ap — ap ) ; in which v is the actual volume under an infin- 

 itely small pressure p, p is the normal pressure, and a is a coeffi- 

 cient, constant, according to Regnault between 1 and 6 atmospheres 

 and according to Amagat, below one atmosphere. When p is one 

 atmosphere and p is indefinitely small, the ratio between the 

 molecular volumes of two gases is v /v' =(l — a)/(l— a'). If 

 their densities be d and d' their molecular masses are propor- 

 tional to (1 — a) d and (1— a') d ! . In the table below, the value of 

 a at 0°, the molecular volume v m at 0° and one atmosphere, the 

 specific gravity d, oxygen being taken as a standard, the molecu- 

 lar mass M when = 32 and the atomic mass fx when O = 16, are 

 given as calculated : 



H N CO 



a —0-00046 +0*00038 +0-00046 +0-00076 



v m 1-00046 0-99962 0-99954 0-99924 



d 0-062865 0'87508 0*87495 1-0 



M 2-01472 28*0132 28*0068 32 



fi 1-0074 14-007 12-007 16 



The author compares the atomic masses of hydrogen, nitrogen, 

 carbon and oxygen deduced as above from the molecular vol- 

 umes and relative densities, with the best determinations of these 

 values by chemical methods, and shows that they are almost 

 identical. 



OH N C 



Physical method, 16 1-0074 14*007 12*007 



Chemical method, 16 1-0023 — 1-0075 14-012 12-001—12-005 



It would appear therefore that not only do the values of the 

 atomic masses obtained from relative density and compressibility 

 confirm the results obtained by chemical methods, but that in 

 some cases they may be taken as the more reliable of the two. — 

 C. R., cxxvi, 954-956, 1030-1033, March, April, 1898. g. e. b. 



2. On the Preparation of Metals and Alloys by means of 

 Aluminum. — The commercial production of aluminum on a 

 large scale has rendered it possible to make use of this metal for 

 the reduction of the oxides and chlorides of other metals. 



