Preheat oven to 325. Grease and flour a 25 cm tube pan. Cream butter, shortening, and sugar together in mixing bowl until light and fluffy. Add eggs one at a time, beating well after each addition. Blend in vanilla. Sift flour, salt, baking powder, and soda together, add to creamed mixture alternately with milk, beginning and ending with flour mixture. Mix well after each addition. Spoon batter into prepared pan. Bake for 1 hour and 15 minutes or until toothpick inserted one inch from edge comes out clean. Cool in pan for 10 minutes; turn out onto wire rack and cool completely. ----