In a non-aluminum stock pot, dissolve 1/3 cup baking soda in 5 cups water. Bring water to a boil, and then remove from heat. Preheat oven to 400 degrees F (200 degrees C).
In a large bowl, sift together all-purpose flour, whole wheat flour, and baking soda. Stir in buttermilk and honey until dough pulls together. Turn dough out onto a lightly floured surface, and knead briefly to form a firm dough.
Divide dough into 12 equal pieces. Roll each piece into a cylinder approximately 12 inches long. Form into classic pretzel shape. Pinch ends to seal. Dip pretzels in baking soda solution and then place on lightly greased cookie sheets.
Sprinkle pretzels with kosher salt, and bake in preheated oven until golden brown, about 10 minutes.