A 3.10g sample of anyhydrous NiSO4 is exposed to moiost air for an extended period of time. At the end of this period, its mass rose to 5.62g, due to pick up of water. Assuming that this represents water of hydration, calculate the value of x in the hydrated salt NiSO4 - xH2O. (molar masses: Ni = 58.69; S = 32.07; O = 16.00; H = 1.008)