]55 ON SUPERACID AND SUBACID SALTS.) 



rated carbonate of soda, and with the same result; for this 

 also becomes a true semicarbonate by being exposed for a 

 short time to a red heat. 



Supersulphate of Potash, 



Supersulphate ^y ^" experiment equally simple, supersulphate of potash 

 of potash. may be shown 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 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 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 supersulphate of potash, which when dissolved in water 

 will be very neai-ly neutralized by an addition of twenty 

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

 nei-ally found very slightly aciH,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 as- 

 purae 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. 



Superoxalate of Potash. 

 Superoxalate Exp. 4. The common superoxalate of potash is a salt 

 of pou&h. ^-^^^ contains alkali sufficient to saturate exactly half of the 

 acid present. Hence, if two equal quantities of salt of sor- 

 rel be taken, and if one of them be exposed to a red heat, 

 the alkali which remains will be found exactly to saturate the 

 redundant acid of the other portion. 



In addition to the preceding corapoimds, selected as dis- 

 tinct examples of binacid salts, I have observed one remark- 

 able iiistance of a more extended and general prevalence of 



the 



