$8 Dr. Wollaston on Super-acid 
Sub-carbonate of Soda. 
Exp. 2. A similar experiment 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 shewn to contain exactly twice as much acid as is ne- 
cessary for the mere saturation of the alkali present. 
Exp. 3. Let twenty grains of carbonate of potash (which 
would be more than neutralized by ten grains of sulphuric 
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 boil, and begins to 
appear slightly red hot, a part of the redundant acid will be 
expelled, and there will remain a determinate quantity form- 
ing 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 generally 
found very slightly acid, in consequence of the small quantity 
of sulphuric acid which remains in the vessel in a gaseous 
state at a red heat. 
In the preceding experiments, the acids are made to assume 
a determinate proportion to their base, by heat which cannot 
destroy them. In those which follow, the proportion which 
a destructible acid shall assume cannot be regulated by the 
same means ; but the constitution of its compounds previously 
formed, may nevertheless be proved with equal facility. 
