1. Hydrochloric acid, or ___, is the main component of gastric acid, which is produced by the parietal cells of the stomach. It is released into the stomach to help keep the pH between 1 and 2 for digestion. A thick mucus layer buffers and protects the stomach tissue itself from the acidic environment. 2. Copper (i) iodide, or ___, is often used as a source of dietary iodine in table salt and animal feed. This is necessary because it is an essential element (needs to be ingested) and it is used in the production of thyroid hormones by higher animals. In fact, 2 billion people suffer from iodine deficiency, which is the leading preventable cause of intellectual disabilities. 3. Sodium fluoride, or ___, is commonly used in the fluoridation of water (although other compounds are now preferred in the US), which helps prevent tooth decay. The CDC (Centers for Disease Control) have listed the fluoridation of water as one of the ten great public health achievements of the 20th century. 4. Potassium chloride, or ___, is an ionic compound used to stop the heart in lethal injections, second-trimester abortion, and third-trimester abortion. The surplus of potassium ions interferes with the sodium-potassium pump, which leads to depolarization and the inability of heart muscle to continue contracting. 5. Calcium chloride, or ___, is a component of Ringer's solution, which is an electrolyte solution used to keep osmotic balance of exposed tissue during surgery.