Which of the following is called white vitriol?

• A

  $\mathrm{Z}\mathrm{n}\mathrm{C}{\mathrm{l}}_2$
• B

  $\mathrm{M}\mathrm{g}\mathrm{S}{\mathrm{O}}_4.7{\mathrm{H}}_2\mathrm{O}$
• Correct answer
  C

  $\mathrm{Z}\mathrm{n}\mathrm{S}{\mathrm{O}}_4.7{\mathrm{H}}_2\mathrm{O}$
• D

  $\mathrm{A}{\mathrm{l}}_2(\mathrm{S}{\mathrm{O}}_4{)}_3$

Hence, the correct answer is option: 'C'.