In 1924, Arm & Hammer distributed a twenty-eight-page booklet to physicians describing sodium bicarbonate as clinical medicine — for influenza, kidney disease, gastric distress, uric acid disturbances, respiratory illness, and the general support of the body's cleansing processes. The same manufacturer cannot legally publish that booklet today. The substance is unchanged. The evidence has only grown. What changed is the regulatory environment, which now restricts what can be said about compounds that cannot be patented. Baking Soda locates sodium bicarbonate inside the terrain framework industrial medicine buried. It maps what the compound does at the level of the blood, the kidneys, the lungs, the digestion, the mouth, the skin, and the acidic tissue that industrial modernity produces. It is clear about what bicarbonate cannot do, and about what must accompany it for the framework to actually work. The compound is cheap. The compound is in every grocery store. The compound is one of the safest substances in general medical and household use. And it has been progressively excluded from the professional medical conversation while remaining freely available to any reader willing to acquire it. Across eighteen chapters and three Q&A appendices, the book covers the physiology, the historical burial of the terrain framework, and the specific applications — respiratory, kidney, digestive, athletic, dental, transdermal (baths), and cancer — where bicarbonate plays its role. It closes with what medicine forgot, and what remains recoverable to any reader willing to work with it.