Modifying the force of Chemical Attraction, 239 
‘‘Berthollet has asserted, indeed, that a large quantity of 
potassa, is capable of separating a a small quantity of sulphur- 
ic acid from the sulphate of barytes; but his experiments 
were made in contact with the atmosphere in which carbon- 
ic acid is always flying about; but it 1s well known that the 
carbonate of potassa and sulphate of baryta, mutually decom- 
pose each other.”*—Davy’s Elements of Chemical Philoso- 
ph 
— appears therefore, that “ the sources of fallacy” ae not 
* escape the observation of Berthollet,” and tha he suppo- 
sed himself to have obviated them, He knew ver a well 
that carbonate of potassa and sulphate of baama mutually 
Saepmapone each other and that carbonic acid is absorbed 
ry potassa, when it is boiled in contact with the atmosphere. 
e took care therefore, to employ such potassa as “ contain- 
ed no carbonic.) aid. and then carried on the process in @ 
acid that could have entered by the beak and travelled along 
the neck of the retort to the materials, must have been in- 
quantity of pa ies of potassa chan could be crys ‘ 
It is obvious nO eric that Berthollet’s experiment did not 
differ from the common process, 7 vented by him, for procur 
ing pure potassa, orca that the retort was filled with the 
vapor of water instead of the vapor of alcohol.t 
* As I have no English copy of the Chemical Philosophy to refer nites I sub- 
join so much of Van ons’ French translation, as is so gr “M. 
Berthollet a posé en fait qu’une grande qu uantité de potasse peu Cecpaer une 
petite quantité d’acide sulphurique eis af = sulfate de fe baryte ; Mais ses e 
must evidently be, if the case be as I have supposed, it is quite natural: but 
that sir Seeneheey Davy should a build an argument, to overturn the theory of 
