6 ORIGINAL COMMUNICATIONS. 
ing experiment. Let us take two portions of caustic potash, 
a base in which the basic characters are more striking than 
in any other. To one, let us add a sufficiency of sulphuric 
acid to extinguish entirely its basic property ; we shall then 
have a neutral body of a saline taste. You will admit it to be a 
salt. Now let us add to the other portion, hydrofluoric acid. 
At a certain point the basic properties of the potash will dis- 
appear, and we shall have a resulting compound quite as 
neutral as the sulphate of potash, endowed with a saline taste 
entirely analogous to that of the sulphate. The basic pro- 
perties of the potash are destroyed by the hydrofluoric acid, 
as well as by the sulphuric acid. But you will allege the 
resulting combination is not a salt, but a base which has ex- 
changed one basifier (oxygen) for another basifier (fluorine.) 
In proof you may add as much more hydrofluoric acid, which 
combining with the new base will form with it a crystallized 
salt. But this salt is not neutral, it has almost the same acidity 
of taste as the hydrofluoric acid employed. The new base 
does not destroy then the acid reaction. 
Let us make a further addition of sulphuric acid to the 
sulphate of potash. A salt equally acid will result, in which the 
sulphate of potash acts the same basic part towards the sul- 
phuric acid, as the fluoride of potassium towards the hydro- 
fluoric acid. Should it be desired to extend the comparison 
further, it will be found that for each less electro-positive 
fluoride, susceptible of combination with the potassic fluoride, 
there will be, with but very few exceptions, a corresponding 
sulphate, susceptible of combination with the sulphate of 
potash. The analogy is then complete, it exists not only in 
the perfect neutrality of the two potassic salts, in their 
saline taste, but also in their manner of forming combinations 
with other bodies; notwithstanding one of them, the sulphate, 
contains one element more than the other. If, instead of 
potash, potassium were employed to saturate our two acids, 
the analogy of the operation in both cases, would be still more 
complete. The same quantity of metal, would displace equal 
volumes of hydrogen. When the visible results of our ex- 
