Intelligence and Miscellaneous Articles, 315 



Exp. 1. 50 grains of pure dry carbonate of potash; prepared by 

 exposing the bi-carbonate to a red heat, are dissolved in 200 grains 

 of water (4 times the weight of the carbonate) ; and to the solution 

 are added 70 grains of proto-hydrate of lime. The mixture is heated 

 to boiling as quickly as possible, the whole heating operation only 

 lasting two minutes. The liquor is filtered while hot and undiluted, 

 and a part of it treated with sulphuric acid, sp. gr. 1*135, of which 

 60 grain measures are required before effervescence takes place, and 

 only 20 more for saturation; consequently fths of the carbonate are 

 decomposed by the lime. 



The boiling point of the mixture is about 220° ; but I find that a 

 very material decomposition of the carbonate takes place even when 

 a like mixture is exposed only to 150° for a quarter of an hour, being 

 briskly agitated all the time. 



Exp. 2. 6 1 '4 grains of pure dry carbonate of potash = 1 atom, are 

 dissolved in 320 grains of water = 40 atoms, or about 5£ times the 

 weight of the carbonate ; and to the solution are added 90 grains of 

 hydrate of lime: 50 grains more water are also added to the mixture 

 as an allowance for the loss in boiling. It is now heated up to boil- 

 ing in 1^- minute, and kept boiling another 14- minute, when it is 

 found by weighing that the additional 50 grains of water have evapo- 

 rated. 



The liquor is filtered while hot and undiluted, and part of it treated 

 with sulphuric acid, such as before, of which 100 grain measures are 

 required before effervescence takes place, and only 5 more for satu- 

 ration. In this case, therefore, the lime has only left T l r part of the 

 carbonate undecomposed. 



Exp. 3. 61*4 grains of pure dry carbonate of potash = 1 atom, 

 are dissolved in 480 grains of water = nearly 8 times the weight of 

 the carbonate, and to the solution are added 90 grains of hydrate of 

 lime : 50 grains more water are also again added to the mixture. It 

 is boiled as before, until the additional 50 grains of water are eva- 

 porated. 



The liquor is filtered while hot and undiluted, and a part of it found 

 to require 105 grain measures of the sulphuric acid for saturation; 

 only a few minute bubbles of carbonic acid being given out. 



It therefore appears that to obtain caustic potash, not fewer than 

 about 53 atoms of water (besides what is combined with the lime to 

 constitute the hydrate,) are sufficient for each atom of the carbonate. 



The atomic weights here made use of are those of Dr. Dalton. 



How M. Liebig arrives at the conclusion that carbonate of potash 

 loses no carbonic acid when dissolved in only 4 times its weight of 

 water, and boiled with slaked lime, I am not aware, except it is from 

 the entertainment of some theoretical views. He explains the matter 

 upon the fact that concentrated potash takes carbonic acid from lime. 

 Though that maybe the case, it is very evident, from the result of my 

 first experiment, that the solution employed is not sufficiently strong 

 to do so. 



Considerable time has now elapsed since the statement in question 

 was announced ; but as nothing contradictory has, as far as I know, 



2 S2 



