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Chemically a salt, barium chloride (BaCl2), consists of the elements barium (Ba) — a silver-white, alkaline-earth metal, and chlorine (Cl) — a highly corrosive, green-yellow, halogen gas. Sulfuric acid is the strongest commercially important acid — an oxy-acid —, which is a powerful dehydrating agent too. Barium chloride and sulfuric acid, if reacted, produce a water-insoluble solid, barium sulfate, plus hydrochloric acid. The reaction of these two substances is written BaCl2 + H2SO4 → BaSO4 + 2 HCl. Due to its physical and chemical properties, barium sulfate is very valuable to the field of medical radiology.
The water-suspension of barium sulfate is used as a radiocontrast agent, which is a substance that makes certain parts of the body show up better on an X-ray. This substance is frequently prepared using the reaction of barium chloride and sulfuric acid, rather than by an alternate reaction process. The substance resulting from this process must remain in suspension through the entire medical procedure and it must be free from contaminants that pose a health hazard or bad taste. Traces of water-soluble barium compounds must not be present, since soluble barium is highly toxic to humans — it is only the sulfate’s exceptional insolubility that allows it to be used. The size of the particles and other suspension characteristics are carefully controlled through the use of ultrafine milling procedures. The liquid is also tested to make sure that it has the right percentage of solids, viscosity, and pH.
Barium chloride and sulfuric acid are relatively cheap, making the barium "milkshake" an inexpensive, effective, and safe way to test body tissues that are normally transparent on X-rays. The suspension product usually contains additives to make it more useful and patient-friendly. These may include suspending agents, preservatives and flavoring agents. Other medical materials may also be employed to supplement the suspension, such as effervescent tablets. Testing occurs on an empty stomach, which, to the hungry patient, may make the flavored milkshake more inviting.
Ingested barium sulfate coats the walls of the digestive tract, highlighting in white what would otherwise appear as a negative image. This is because barium sulfate absorbs X-rays. Gastrointestinal tract abnormalities, including tumors, pouches and constrictions become apparent — hernias and ulcers can be detected too. No second substance must be consumed or injected to remove barium from the system; barium sulfate is excreted, naturally, mixed in with the feces. How much safer the suspension product manufactured from barium chloride and sulfuric acid is, than the formerly used, costly and carcinogenic thorium-based radio-contrast agents.