A water solution contains 60% Na2S2O2 together with 1% soluble impurity. Upon cooling to 10oC, Na2S2O2· 5H2O crystallizes out. The solubility ofthis hydrate is 1.4Ib Na2S2O2· 5H2O/lb crystal free water.
The crystals removed carry as adhering solution 0.06 lbsolution/lb crystals. When dried to remove theremaining water (but not the water of hydration), the final dry Na2S2O2· 5H2O crystals must not contain more than 0.1 %impurity. To meetthis specification, the original solution, before cooling, is further diluted with water, On the basis of 100 lb of the original solution, calculate:
(a) The amount of water added before cooling.
(b) The percentage recovery of the Na2S2O2in the dried hydrated crystals.