In 1835, the British mathematician William Henry Fox Talbot (1800–1877) made the first permanent paper negative from paper coated with silver nitrate and common table salt ( sodium chloride). In 1802, Thomas Wedgwood (1771–1805), son of the founder of the famous Wedgwood pottery company, used silver nitrate to make temporary negative prints on paper, producing shades of gray as well as pure black and white. That simple discovery formed the basis of the modern science of photography. Schulze found that a mixture of silver, nitric acid, and chalk turns purple or black when exposed to light. The use of silver nitrate in printing and photography dates to discoveries made in the 1720s by the German chemist Johann Schulze (1687–1744). In 1881, the German physician Carl Crede (1819–1892) developed the practice of applying a 2 percent solution of silver nitrate to the eyes of newborn babies to prevent gonorrheal ophthalmia, a bacterial infection of the eyes that may result in blindness in a child. Both the Greeks and Romans, for example, used aqueous solutions of silver nitrate to treat wounds and cuts. The therapeutic effects of silver compounds, including silver nitrate, have been known for many centuries. Soluble in water, glycerol, and hot ethyl alcohol moderately soluble in acetone Silver nitrate is the most widely used of all silver compounds, finding application in the synthesis of other silver compounds, as a catalyst in certain industrial chemical reactions, as an antiseptic and germicide, and in photographic processes. In pure form, the compound is not affected by light, but trace amounts of organic impurities may catalyze the conversion of silver ions (Ag + silver atoms with a positive charge) to grayish neutral silver atoms (Ag 0) that give the salt a grayish tint. Silver nitrate (SILL-ver NYE-trate) is a colorless to transparent to white crystalline solid with no odor and a bitter metallic taste.
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