And so did you. K2SO3 does not raise the temperature of the solution as it is being dissolved. I frankly do not care if you understand my expressions. The fact of the matter, however you express it, is that the potassium sulphite I have is not as soluble as the potassium sulphite Ian has. I do have a good triple beam balance and I do know how to use it. I learned how to read at a very early age as the son of an English Professor, certainly well enough to read the label on the container from PF that proclaims it to contain potassium sulfite. Maybe the non-British spelling is the problem, but I doubt it.
What I specified the first time was weight of solute per volume of solvent. I could specify the weight of solute per weight of solution by simply adding solute to solvent to get total weight, which in any case would be a more precise way of specifying the solution. Weight of solvent per volume of solution changes with temperature due to expansion or contraction.