Mixing baking soda and white vinegar is not harmful as long as it is in an open space; a closed reaction vessel could produce an explosion. Mixing baking soda and white vinegar creates a chemical reaction, the product of which is non-toxic and harmless sodium bicarbonate. Sodium bicarbonate is rapidly converted to carbon dioxide and water; the carbon dioxide spills out over time and eventually only water remains. If some of the sodium bicarbonate or baking soda is left over, it can cause a portion of the solution to be acidic or alkaline. If sodium bicarbonate baking soda and acetic acid are put together in a closed container, the large amount of carbon dioxide released may cause an explosion. So this kind of behavior is not really necessary as it neither produces new magical substances nor new effects.