Baking Soda will raise Alk, but not pH. To make a good buffer that will do both, use a 6:1 ratio of baking soda to washing soda (Arm & Hammer Super Baking soda). It is available in most HEB's on the aisle with the laundry detergent. Chemically it is sodium carbonate. This mixture is basically what you are buying when get any of the commercial aquarium solid buffers. Add some high priced water and you have the A part of a two part additive.

Gary