Method of washing polycrystalline silicon, apparatus for washing polycrystalline silicon, and method of producing polycrystalline silicon

A method of washing polycrystalline silicon comprising:

• a step of acid cleaning in which the polycrystalline silicon is cleaned with an acid solution;
• and
• a step of water cleaning in which the polycrystalline silicon is cleaned with pure water after the step of acid cleaning,
• wherein, residual of the acid solution on a surface of the polycrystalline silicon is removed by immersing the polycrystalline silicon in pure water held in a water cleaning bath, and replacing the pure water in the water cleaning bath at least once, in the step of water cleaning;
• an electrical conductivity C of the pure water in the water cleaning bath is measured after allowing the polycrystalline silicon to stand and to remain immersed in the replaced pure water, for at least 2 hours;
• and
• the step of the water cleaning is finished after the electrical conductivity C of the pure water becomes 2 μS/cm or lower.