312 On the Alkalies of Commerce. 



spective quantities of carbonic acid which are found in the 

 supersaturated carbonate of potash and in the carbonate of 

 lime, we shall see ihat four-tenths of lime must be always 

 sufficient for taking up all the carbonic acid contained in any 

 given quanlity of the best potash of commtrce. 



But here is a double experiment, which we may verify: 

 Take of quicklime, 4 parts; of white potash of Russia, 10 

 parts; pure water, 70 parts : slake the lime with a portion 

 of the water, and dissolve the potash in the remainder: af- 

 terwards mix the whole, boil it for a few minutes, thea 

 allow it to cool, and restore the whole of the 24 parts, which 

 mav have been diminished by the slaking of the lime and the 

 ebullition ; mix the added water very minutely ; allow the 

 whole to subside, and decant a little of the liquor : you will 

 find, upon trying it, that no precipitate is formed in the lime 

 water, and that it makes no efflorescence with the acids. 



In the second place, take the same proportions of lime 

 and potash, but add only 50 parts of water to it ; then try 

 the liquor which will result from this, and you will find that 

 it occasions a precipitate in lime water and an effervescence 

 with the acids. Finally, add 20 additional parts of water to 

 the first 50, and mix the whole carefully : the liquor, when 

 decanted, will occasion neither precipitate nor eflcrvescence : 

 in a word, the alkali will have become caustic inconsequence 

 of the extraction of all its carbonic acid. 



I am inclined to think that this observation maybe use- 

 fully applied to the caustification of soda. 



Explanation of the Cmises of the Uncei-tainty in the Pro- 

 cesses of Caustification. 



We now see clearly the reason why we cannot obtain a 

 pcrf*ictly caustic alkali, if we do not add a sufficient quantity 

 of water to the mixture of lime and supersaturated carbonate 

 of potash. Although it might be tliought we have used too 

 much lime already, yet we must put still more into the mix- 

 ture ; but as it night become too thick, we are under the 

 necessity of adding a new portion of water, which alone 

 com))letes the caustification, although this has been, never* 

 Ibeless, attributed to the new addition of lime. 



Lastly, 



