Dr. Wollaston on Super-acid and Sub-acid Salts. 
However, since those who are desirous of ascertaining the 
justness of this observation by experiment, may be deterred 
by the difficulties that we meet with in attempting to deter- 
mine with precision the constitution of gaseous bodies, for the 
explanation of which Mr. Dalton’s theory was first con- 
ceived, and since some persons may imagine that the results 
of former experiments on such bodies do not accord suffi- 
ciently to authorize the adoption of a new hypothesis, it may 
be worth while to describe a few experiments, each of which 
may be performed with the utmost facility, and each of which 
affords the most direct proof of the proportional redundance 
or deficiency of acid in the several salts employed. 
Sub-carbonate of Potash. 
Exp. 1. Sub-carbonate of potash recently prepared, is one 
instance of an alkali having one-half the quantity of acid ne- 
cessary for its saturation, as may thus be satisfactorily 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 mercury, and let 
the gas be extricated from it by a sufficient quantity of muriatic 
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 ; 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 found to occupy exactly the same 
space, as the quantity before obtained from two grains of fully 
saturated carbonate. 
MDCCCVIir. 
O 
