Barium is a soft, heavy, silver-colored metallic element. This element does not have very many uses outside of the laboratory, but it combines easily with other chemicals to form compounds used for important industrial uses. For example, barium carbonate is used in the manufacture of ceramics and special glasses, but also to purify certain chemical solutions. It is also an ingredient in clay muds, also known as water muds, used in oil well drilling. Barium titanate is used in sonar detectors and other electrical equipment. At low doses, barium acts as a muscle stimulant and at higher doses it affects the nervous system, eventually leading to paralysis. Acute and subchronic oral doses of barium cause vomiting and diarrhea, followed by decreased heart rate and elevated blood pressure. Higher doses cause heart irregularities, weakness, tremor, anxiety, and dyspnea. A drop in serum potassium may explain some of the symptoms. Death can occur from cardiac and respiratory failure. Acute doses of approximately 0.8 grams can be fatal to humans. Barium nitrate causes flares to burn with a green flame. Barium ferrite is used to make magnets. Barium sulfate is an extremely insoluble and non-toxic barium compound. Doctors use it during X-ray examinations of a patient's digestive system. Barium sulfate absorbs the x-rays to show the outline of the intestines on the developed film. A barium enema is performed to examine the walls of the colon. During the procedure, a well-lubricated enema tube is gently inserted into the rectum. The barium can then flow into the colon. The flow of barium is monitored by the healthcare provider on an x-ray fluoroscope screen. The test is used to detect colon cancer. Barium enema can also be used to diagnose and assess the extent of inflammatory bowel disease. Barium sulfate and zinc sulfide form lithopone, a white coloring matter for paint. Barium is never found in its pure state because it combines so easily with other elements. Pure barium is made by passing an electric current through a molten barium compound, such as barium chloride. A piece of barium metal reacts quickly with oxygen and water vapor in the air to form barium oxide. It must be stored under kerosene to keep it pure. Barium is most commonly found as barium sulfate in the mineral barite. The chemical symbol for barium is Ba.