Silver iodide crystals

A To divert storms, clouds can be seeded with silver iodide crystals to promote "targeted" rain. 

Silver iodide particles in aqueous suspension are in equilibrium with a saturated solution of which the solubility product, aAg+ai, is about 10 16 at room temperature. With excess 1 ions, the silver iodide particles are negatively charged and with sufficient excess Ag+ ions, they are positively charged. The zero point of charge is not at pAg 8 but is displaced to pAg 5.5 (pi 10.5), because the smaller and more mobile Ag+ ions are held less strongly than-the 1 ions in the silver iodide crystal lattice. The silver and iodide ions are referred to as potential-determining ions, since their concentrations determine the electric potential at the particle surface. Silver iodide sols have been used extensively for testing electric double layer and colloid stability theories. 

Sometimes, too much rain falls in one location and too little rain falls in another. People have been trying to produce rain on demand for centuries. Because most clouds exist at temperatures below the freezing point of water, rain often begins when water vapor deposits on ice crystals. (When ice crystals approach the surface of Earth, they melt and fall as rain if the temperature of the air near the surface is above freezing.) Rainmakers focus on the crucial role played by ice crystals. For example, dry ice pellets can be dropped into a cloud. The cold dry ice cools the water vapor in the cloud and ice crystals form. Sometimes tiny silver iodide crystals are sprayed into a cloud to serve as artificial "ice pellets."... 

As a way of holding silver halide (silver bromide and silver iodide) crystals in place on photographic films and plates ... 

The very large ionic conductivity of silver iodide crystal is explained by its structure. The crystal is cubic, with the four iodide ions in the unit cell in the close-packed positions 00 0, (Figure 2-7). The... 

A silver iodide crystal has a surface pattern that closely resembles that of an ice crystal it was this resemblance that led Langmuir to try silver iodide as a seeding material. The silver atoms and iodine atoms occupy the positions of alternate oxygen atoms in the ice structure (Figure 9-8), and the silver-iodine distance, 280 pm, is only 1.5 percent greater than the oxygen-oxygen distance in ice. 

A commercial process that uses a quinone is black-and-white photography. Black-and-white film is coated with an emulsion containing silver bromide or silver iodide crystals, which become activated by exposure to light. The activated silver ions are reduced in the developing stage to metallic silver by hydroquinone, which at the same time is oxidized to quinone. Following is an equation showing the relationship between these species. 

A 10.0-mL sample of potassium iodide solution was analyzed by adding an excess of silver nitrate solution to produce silver iodide crystals, which were filtered from the solution. 

S. V. Shevkunov, Structure of water in microscopic fractures of a silver iodide crystal, Russ. J. Phys. Chem. A, 88,313-319 (2014). 

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