Who first discovered that silver nitrate turns black after being irradiated by sunlight and used it to image?

It was shulte who first discovered that silver nitrate would turn black after being irradiated by sunlight, and used it to image. Silver nitrate is a colorless crystal, which is easily soluble in water. Pure silver nitrate is stable to light, but its aqueous solution and solid are often stored in brown reagent bottle due to the lack of purity of general products.

If chloride ion, bromine ion and iodine ion are encountered, they will react to generate water-insoluble and nitric acid-insoluble silver chloride (white precipitate), silver bromide (light yellow precipitate) and silver iodide (yellow precipitate). Therefore, it is often used to test the presence of chloride ions;

Ag？ (aq) + Cl？ (aq) → AgCl(s)

Silver chloride forms a gray solution under light. Silver chloride can react with ammonia water and re-dissolve to generate colorless silver (I) diammonium solution;

AgCl +2NH？ → Ag(NH？ )2? + Cl？

Extended data:

Silver nitrate will turn gray-black when it meets organic matter and decompose into silver. Pure silver nitrate is stable to light, but its aqueous solution and solid are often stored in brown reagent bottle due to the lack of purity of general products. When silver nitrate is heated to 440℃, it is decomposed into silver, nitrogen, oxygen and nitrogen dioxide.

The aqueous solution and ethanol solution are neutral to litmus, and the pH value is about 6. The boiling point is 444℃ (decomposition). It is oxidizing. In the presence of organic matter, light will turn gray or gray-black. Silver nitrate can precipitate or coordinate with a series of reagents (see coordination compounds).

The ammonia solution of silver nitrate can be reduced by organic reducing agents aldehyde and sugar. Therefore, it is a reagent for detecting aldehydes and sugars. It is also used to determine chloride ion, catalyst for manganese determination, electroplating, photography and porcelain coloring.

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