Here is a fair explanation stripped from waiakeasprings...
"A lot of brands are adding baking soda (sodium bicarbonate) to their bottled water. "But why?", you may ask. Well for starters, sodium bicarbonate is a way to create a higher pH, or alkalinity, in drinking water. Sodium bicarbonate is known as nahcolite, which is part of the natural mineral natron. Natron, which contains large amounts of sodium bicarbonate, has been used since ancient times and has various health benefits. Many waters with a pH <6.5 are acidic, soft, and corrosive. Thus, sodium compounds like sodium bicarbonate are added during water treatment in order to raise the pH of the water by chemically neutralizing the acidity as well as to soften the water. - https://waiakeasprings.com/blogs/content/why-brands-are-adding-baking-soda-to-their-water-what-you-should-know-about-it/"
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No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)