What compound is used as a contrast agent for x-rays of the gastrointestinal tract?

Barium sulfate is the compound used as a contrast agent for x-rays of the gastrointestinal tract due to its specific properties that allow it to absorb x-rays effectively. When ingested, barium sulfate fills the gastrointestinal tract and provides a clear outline of the internal structures, which helps in the diagnosis of various conditions such as blockages, tumors, or ulcers.

This compound is chosen because it is relatively inert and does not get absorbed into the body, reducing the risk of toxicity. Its high atomic number enables it to stand out against surrounding tissues in x-ray images, leading to improved visibility of the gastrointestinal anatomy.

On the other hand, iron chloride, calcium carbonate, and magnesium hydroxide do not have the same properties that make them suitable as contrast agents for x-ray imaging. Iron chloride is primarily used in other applications, calcium carbonate is used for various nutritional and medicinal purposes, and magnesium hydroxide is commonly utilized as an antacid or laxative, but not in radiographic imaging.