244- Mr. Hennell on the mutual action of 
crystals were heated in a tube, when they fused, swelled up, 
and gave off a dense white vapour, which condensed into an 
oil-like fluid, smelling strongly of sulphurous acid ; the re- 
siduary salt was an acid sulphate of potash. 
The following experiments were now undertaken with a 
view of more accurately determining the composition of this 
crystalline salt. 
20 grains of the crystals being heated to redness, left 
10 ,56 grains of sulphate of potassa, equal to 4,8 sulphuric 
acid, 5,7 6 potash. 20 grains were dissolved in a solution of 
caustic potash, boiled to dryness, heated red hot, when cold 
dissolved in distilled water, the excess of potash saturated 
by nitric acid, and the solution added to one of muriate of 
baryta ; 28 grains of sulphate of baryta were obtained, very 
nearly equal to 9,6 sulphuric acid ; the salt therefore con- 
tained twice the quantity of sulphuric acid required to form 
a neutral sulphate with the potash, -or two proportionals. 
In order to ascertain the proportions of the remaining 
elements of the salt, 5 grains were heated with oxide of 
copper, 5,5 cubic inches of carbonic acid gas, and 1,4 grains 
of water were collected ; several of these experiments were 
made with similar results ; 20 grains of the salt had been 
found to contain 5,76 potash, 
9,60 sulphuric acid. 
5 grains therefore must have contained 1,44 potash. 
2,40 sulphuric acid. 
5,5 cubic inches carbonic acid gas contain 0,699 carbon. 
The water obtained was 1 ,40. 
5,939 grains. 
