PRODUCED BY BODIES ACTING BY CONTACT. 15 
with a second, and the compound which results enters into com- 
bination with a third body. 
Sulphurous acid has more affinity for oxygen than the binoxide 
of nitrogen; however, sulphurous acid does not combine with 
oxygen when the mixture of these gases is left in contact for a 
very long time, whereas the binoxide of nitrogen seizes directly 
on the gaseous oxygen to form hyponitric acid. This yields its 
oxygen to the sulphurous acid and becomes again binoxide of 
nitrogen. The oxygen therefore is, in the hyponitric acid, in 
such a state that it can combine with the sulphurous acid. On 
placing a mixture of oxygen and sulphurous acid in presence of 
platina sponge, these two gases combine: the action of the pla- 
tina is therefore here again the same as in the case of hydrogen 
and oxygen. ' 
All the processes, and especially the production of the zthers, 
and of zther itself, lead to the conclusion that chemical decom- 
positions and combinations may be impeded by the respective 
position of the atoms; but that the force of attraction which 
certain bodies exercise upon the atoms of those with which they 
are in contact, may change the position, so as to determine che- 
mical reactions. The manner in which gases behave towards 
charcoal, and especially towards platinum black, proves that this 
attraction is very strong, even with regard to bodies of a different 
nature. 
M. Berzelius has given to this force the name of catalytic 
force, with as much reason as the expression ‘force of affinity,’ 
&c. has been employed, and understands by this term a force 
which is peculiar to several bodies which do not intervene che- 
mically in the reactions which they determine, and the activity 
of which consists in destroying chemical combinations. To con- 
nect the name with the phenomena, I have named these sub- 
stances contact substances, and the chemical process, decompo- 
sition or combination by contact. 
