Barium is a soft, heavy, silver-colored metallic element. This element does not have many uses outside of the laboratory, but it easily combines with other chemicals to form compounds used for important industrial uses. For example, barium carbonate is used in the production of ceramics and specialty glasses, and also to purify some 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 ultimately leading to paralysis. Acute and subchronic oral doses of barium cause vomiting and diarrhea, followed by decreased heart rate and increased blood pressure. Higher doses cause cardiac irregularities, weakness, tremors, anxiety and shortness of breath. A drop in serum potassium may explain some of the symptoms. Death may occur from cardiac and respiratory failure. Acute doses around 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-poisonous barium compound. Doctors use it in X-ray examinations of a patient's digestive system. Barium sulfate absorbs X-rays to show the outline of the intestine 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 is then allowed to flow into the colon. The flow of barium is monitored by the healthcare provider on an X-ray fluoroscopic screen. The test is used to detect colon cancer. The barium enema can also be used to diagnose and evaluate the extent of inflammatory bowel disease. Barium sulfate and zinc sulfide form lithopone, a white coloring substance for paint. Barium is never found in its pure state because it easily combines with other elements. Pure barium is obtained by passing an electric current through a molten barium compound, such as barium chloride. A piece of barium metal quickly reacts 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 often found as barium sulfate in the mineral barite. The chemical symbol for barium is Ba.