On the Alkalies of Commerce. £51 



acid and potas^h are constantly the same; so that 100 parts 

 of sulphuric acid always displace by their saturation only 

 forty parts of carbonic acid, when \vc employ any of the 

 potashes of commerce ; while, if we saturate these same 100 

 parts of sulphuric acid by truly neutral carbonate of potash, 

 we constantly displace 84 parts of carbonic acid. We know 

 that heat takes from the carbonate of potash only a portion 

 of its acid ; I am therefore inclined to think that this quan- 

 tity of carbonic acid remaining in the potash of commerce 

 is constant, which even the heat of incineration cannot di- 

 minish ; it is probable that, after having exposed carbonate 

 of potash to this degree of heat, we shall find that it has not 

 retained either more or less of carbonic acid than the potash 

 pf commerce, relatively to the alkali-metrical degrees re- 

 gpcctively found in these salts. 



Chemists who repeat these experiments will find that 

 pearlashes give a less proportion of carbonic acid : it is pro- 

 bable that this is to be attributed to some circumstances of 

 the process during which the ashes or the ley has absorbed 

 a little less of the carbonic acid, \\.hich is both formed 

 during combustion and is found in the atmosphere. This 

 slight ^lifference would explain why some manufacturers 

 prefer the white potash of Russia to pearlashes. Thus, al- 

 though a long exposure to the air may increase the propor- 

 tion of carbonic acid in the potash of commerce, this does 

 not pjievent us from distinguishing two constant states of 

 the carbonate of potash by applying this name to the truly 

 neutral carbonate only, and by denominating the potash of 

 commerce supersaturated carbonate fif potash: this is con- 

 formable to the principles of the chemical nomenclature, as 

 the borax of commerce with an excess of base has been 

 called supersaturated borate of soda. I admit that between 

 these two slates of carbonate of potash and sxipersaturated 

 carbonate of potash we may create intermediate degrees in 

 all proportions, when by combining the carbonic acid with 

 the latter we stop before having saturated all the alkali. 



Some authors have, designated as alkaline carbonate of 

 potash the salt with an excess of base, to which I nuist call 

 the attention of chemists J but although this denomination 



may 



