Combine flour and salt in a large mixing bowl; cut in butter and lard with a pastry blender until mixture resembles coarse meal. Set aside.
Dissolve soda in water; stir well, and set aside.
Beat eggs in a large mixing bowl until foamy; add sugar and dissolved soda mixture, beating well. Stir in vanilla. Gradually add reserved flour mixture, stirring until well blended. Cover and chill thoroughly.
Roll dough to 1/2-inch thickness on a lightly floured surface; cut with a 2-inch round cookie cutter. Place 2 inches apart on lightly greased cookie sheets. Bake at 400° for 7 minutes. Remove from cookie sheets, and cool on wire racks.