SCIENTIFIC SUMMARY. 
203 
Contributions to Chemical Dynamics. — Dr. Wright and Mr. Luff have 
furnished a second report to the Chemical Society on some points in chemical 
dynamics, and containing an account of some further researches on the in- 
fluence of time and temperature on the decomposition of metallic oxides by 
the three agents — carbon, carbonic oxide, and hydrogen. In their earlier 
report they studied the action of these three substances on ferric and 
cupric oxides, with the result that, for similar physical conditions of the 
reacting bodies, the greater the heat-evolution which occurs when the two 
substances react, the lower is the temperature at which the reaction com- 
mences. In the present report Dr. Wright and Mr. Luff investigate the 
action of carbon, carbonic oxide, and hydrogen on a number of additional 
metallic oxides, including those of manganese, lead, cobalt, and nickel. They 
arrive at the following conclusions. In the case of the oxides of iron and 
copper, which form two definite series of salts, the temperature of initial 
action of the reducing agents on the two oxides corresponding to these series 
of salts will be the same for each. This is in accord with the fact that the 
same amount of heat is evolved in the conversion of a given volume of 
oxygen into either of these oxides. In the case of the oxides of the metals 
— manganese, lead, nickel, and cobalt — which form superoxides, not corre- 
sponding with definite series of salts, and evolving oxygen on being heated, the 
temperature of initial action of a given reducing agent on the superoxide of 
one of these metals is sensibly lower than that of the same agent on the 
stable monoxide of the same metal. It is probable that this difference indi- 
cates that less heat is evolved when a given amount of oxygen unites with 
the metal to form the superoxide than would be the case if the monoxide was 
formed, which indeed is known to be the case in connection with one of 
these metals — manganese. It was also found that the temperature at which 
carbonic oxide commenced to act on any metallic oxide was invariably less 
than that required for hydrogen to react ; whilst we learn that hydrogen com- 
menced at a lower temperature than required by carbon. The connection 
which has thus been established between the amount of heat evolved during 
a reaction and the temperature at which the reaction occurs is a point of 
very great interest in chemical dynamics, and in the hands of the mathema- 
tician may lead to important light being thrown on the true nature of 
chemical combinations. It points in an obvious manner to an imaginable 
connection between the velocity of molecular vibration and the attractive 
force maintaining chemical union. This idea is strengthened by the remark- 
able fact to which the authors draw attention, that a long-continued 
exposure of the metallic oxide to the action of the reducing agent will 
develop a sensible chemical reaction at a lower temperature than will give 
rise to any action in a few minutes. It is to researches of this nature that 
we must look for a real extension of our present slight knowledge of the 
Dynamics of Chemistry. 
The Yttrium Group of Metals . — In 1843 Mosander announced that Ber- 
zelius’s yttria was really a mixture of three earths which he named yttria, 
erbia, and terbia, and he gave a short account of the characteristics of each 
base. Yttria was colourless and afforded colourless salts ; terbia was also 
colourless, but gave pink salts ; and erbia was dark yellow. Subsequently 
Berlin, and afterwards Bunsen and Balir, worked on this subject, but were 
