I am looking for a cheap chemical that is very highly soluble in water, such that it can raise the density of water to about 5 or 6 kg per liter. The resulting solution, however, cannot be viscous as buoyant forces will need to perform in the solution. I've been doing research and I've found conflicting values for the solubility of certain compounds such as Iron(III) Sulfate. One site gives the solubility as 4.4kg/liter while on another page, states that it is only slightly soluble. I've also considered fructose although viscosity would be a problem at the density I require. Could you please recommend a few non-toxic (skin contact will probably be required) substances that are not expensive in bulk as I will have to saturate a solution of about 100 liters of water.
Thank you kindly.