Where can I find Baking soda in Arth?

Baking soda can also be found in these cities:

Baar Buchrain Buochs Cham Ebikon Einsiedeln Emmen Goldau Horw Ibach SZ Ingenbohl Kriens Küssnacht Lucerne Richterswil Rotkreuz ZG Stans Steinhausen Stäfa Unterägeri Urswil Wädenswil Zug

You can also find this in Arth:

Desserts Dessert Baking Mixes Cake Glaze Peanut Butter Ice Cream Rice Dishes Vegetable Juices Instant Iced Coffee Cheese Roll Canned Fish