JP2934863B

PURPOSE:To provide the title unit having high purity and high permeability, enhanced in chemical resistance and easy to prepare by constituting the whole of the unit of high purity silica glass and performing the mutual bonding of a casing and a filter by welding. CONSTITUTION:A bottomed cylindrical filter 7 is fixed to the interior of a cylindrical casing 1 having a supply part 3 and a discharge port 5 so as to cover the discharge port 5. The casing 1 is constituted of non-crystalline silica with purity of 99.9% or more containing alkali, alkali metal, heavy metals and an element of the Group BIII in the total amount of 150ppm or less. The filter 7 is constituted by forming a fine filter layer composed of a sintered body of a non-crystalline silica powder with the same purity to the outer or inner periphery of a porous cylindrical support composed of the non-crystalline silica powder with the same purity and forming the bottom part of the support from a non-crystalline silica plate having the same constitution or purity. As a result, chemical resistance is enhanced and manufacturing becomes easy.