Calcium carbonate is chemically related to the much more common household chemical sodium bicarbonate, or baking soda. While the latter helps to regulate the pH of the blood both as part of the body's natural pH-controlling system and when given as a medication, the former isn't used to neutralize the blood's pH.
Calcium Carbonate
Calcium carbonate, which has the chemical formula CaCO3, is very common in nature. it is the major component of limestone and marble, it's found in many different aquatic and terrestrial organism shells, and it's the major component of classroom chalk. It's not very soluble in water, though it dissolves well in acidic solution because carbonate -- CO3 -- can react with acid to make bicarbonate, which is HCO3, and eventually to make carbonic acid, which is H2CO3.
Neutralization of Acid
Because carbonate from calcium carbonate reacts with acid, calcium carbonate is a common antacid medication. When you take calcium carbonate antacid, the calcium and carbonate particles separate from one another in your stomach. The carbonate reacts with -- and neutralizes -- acid to make carbonic acid, which then decomposes into water and carbon dioxide. In this way, calcium carbonate is an effective means for getting rid of excess stomach acid.
In Dialysate
Calcium carbonate is sometimes incorporated into dialysis solution; according to Dr. A Hutchison and colleagues in a 1992 article published in the journal "Nephrology Dialysis Transplantation," it's used to bind to excess phosphate, which is a reaction in which calcium participates. The related compound sodium bicarbonate, however, is sometimes used in dialysate as a means of helping to neutralize fluid pH. Sodium bicarbonate is a buffer, meaning that it helps to keep the pH of biological fluid near neutral, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry."
Neutrality
On the pH scale, "neutral" refers to a pH of 7. The blood is actually slightly basic of neutral, with a pH of 7.4, explain Garrett and Grisham. It is not beneficial to neutralize, or lower, that pH; attempting to do so actually creates the potential for acidosis, which has severe metabolic consequences, and the body resists the change strongly. If you have a blood pH that is significantly different from 7.4, you'll need medical treatment in order to bring it back to normal again.
References
- "Nephrology Dialysis Transplantation"; Low-calcium dialysis fluid and oral calcium carbonate in CAPD.A method of controlling hyperphosphataemia whilst minimizing aluminium exposure and hypercalcaemia; A. Hutchison et al; 1992
- “Biochemistry”; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
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