mg cristalohidrat +x g h2O=250g sol
in care exista : 140g sol...........40g sare
250g sol...........x=71,43g sare
250g ch.........160g sare anhidra
y g ch.............71,43g sare y=111,6 g CuSO4*5H2O
masa de apa adaugata este :
250g - 111,6g = 138,4g.