A water solution contains 62% Na2S22 together with 1.4% solubleimpurity. The sol

A water solution contains 62% Na2S22 together with 1.4% solubleimpurity. The solution is first diluted with water and then cooledto 10 degrees Celsius where Na2S2O2.5h20 crystallises out. Thesolubility of this hydrate at 10 degrees is 1.4 lb Na2S2O2.5H20 /lb free water. The crystals are then separated in the first stagefilter and carry an adhering solution in the proportion: 0.058 lbsolution / lb crystals. The separated crystals are then dried in asecond stage to remove the remaining free water (but not the waterof hydration). If the final dry Na2S2O2.5h20 crystals must notcontain more than 0.18wt% impurity calculate: The amount of wateradded before cooling and the percentage recovery of the driedcrystals.