Sodium chloride infrared-transparent material

The infrared spectrum of a liquid may conveniently be recorded as a thin film of the substance held in the infrared beam between two infrared-transparent discs without the need for a diluting solvent. It is customary to use polished plates of sodium chloride as the support material this material is adequately transparent in the region 2-15 /im. Spectra in the longer wavelength region (12-25 m) can be recorded using potassium bromide plates. Sealed cells (p. 267) should be used for volatile liquids. 

In a simple transmission experiment the liquid sample is examined in a cell made of a suitable infrared transparent medium. These include sodium chloride, potassium bromide, zinc selenide, cadmium telluride, and germanium. Materials like sodium chloride should not be used to study solutions in protic solvents like methanol and water. 

It is very important to make the right choice of the cuvette material for liquid and gas samples. This material must be transparent to the infrared light. Sodium chloride is the most often used material for the cuvettes and the optics of the infrared spectrometer. Other material such as special types of glass, quartz, aluminum oxide, calcium chloride, potassium bromide and so on are also used for special purposes. 

The material of the prism is important in infrared spectroscopy, since it must be transparent to infrared light. The material most frequently used for analysis in the middle wavelength region is sodium chloride. Prism materials for the analysis of short and long wave infrared light are usually potassium bromide, cesium bromide, and cesium iodide. 

An important consideration in the choice of infrared cells is the type of. window material to be used. The material must be transparent to the incident infrared radiation and thus alkali halides are normally used in transmission methods. The cheapest material is sodium chloride (NaCl), with other commonly used materials being listed in Table 3.2a. ... 

Sample handling also presents a number of problems in the infrared region. For example, there is no rugged window material for cuvettes that is transparent and also inert over this region. The alkali halides are widely used, particularly sodium chloride, which is transparent at wavelengths as long as 625 cm. For frequencies less than 600 cm, polyethylene cells are frequently used. 

Infrared window A material that has a high transparency for IR radiation over some portion of the IR spectrum. Examples Sodium chloride silicon germanium potassium bromide (KBr) cesium iodide high density polyethylene. 

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