On Super -acid and Sal-acid Salts. 27f 



Sub-carhonate of Px^tash, 



ExperiTnent I. Sub-carbonaie of potash recently prepared, 

 IS one instance of an alkali having one half the quantity of 

 acid necessary for its saturation, as may jhus be satisfap- 

 torily proved. 



Let two grains of fully saturated and well crystallized car- 

 bonate of potash be wrapped in a piece of thin paper, and 

 passed up into an inverted tube filled with niercury, and let 

 the gas be extricated from it by a sufficient quantity of mu- 

 riatic acid, so that the space it occupies may be marked 

 upon the tube. 



Next, let four grains of the same carbonate be exposed 

 for a short time to a red heat j and it will be found to have 

 parted with exactly half its gas ; for the gas extricated from 

 it in the same apparatus will be tound to occupy exactly the 

 same space as the quantity before obtained froni two grains 

 of fidly saturated carbonate. 



Sul-cailonate of Soda. 

 Experiment II. A similar expcnnient may be made with 

 a saturated carbonate of soda, and with the same result; for 

 this also becomes a true semi-carbonate by being exposed 

 for a short time to a red heat. 



Super-sulphate of Potash. 



By an experiment equally simple, super-sulphate of potash 

 may be shown to contain exactly twice as much acid as is 

 necessary for the mere saturation of the alkali present. 



Experiment III. Let twenty grains of carbonate of potash 

 (which would be more than neutralized by ten grains of sul- 

 phuric acid) be mixed with about twenty-five grains of that 

 acid in a covered crucible of platina, or in a glass tube three 

 quarters of an inch diameter, and five or six inches long. 



By heating this mixture till it ceases to bod, and begins 

 to appear slightly red hot, a part of the redundant acid will 

 be expelled, and there will remain a deternnnate quantity 

 forming super-sulphate of potash, which when dissolved in 

 water will be very nearly neutralized by an addition of twenty 

 grains more of the same carbonate of potash ; but it is ge- 

 nerally found very slightly acid, in consequence of the small 



S 'i quauiity 



