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Sometimes a humidity indicator is included in the desiccant to show, by color changes, the degree of water-saturation of the desiccant. One commonly used indicator is cobalt chloride (CoCl 2), which is blue when anhydrous, but turns purple upon bonding with two water molecules (CoCl 2 ·2 H 2 O).
A vacuum desiccator (left) and desiccator (right). Silica gel with cobalt chloride indicator placed in the lower shelf is used as the desiccant.. A desiccator is a heavy glass or plastic container, now somewhat antiquated, used in practical chemistry for drying or keeping small amounts of materials very dry.
Calcium chloride; Calcium hydride; Calcium oxide; Calcium sulfate (Drierite) Cobalt(II) chloride; Copper(II) sulfate; Lithium chloride; Lithium bromide; Magnesium ...
When a visible indication of the moisture content of the silica gel is required, ammonium tetrachlorocobaltate(II) (NH 4) 2 [CoCl 4] or cobalt(II) chloride CoCl 2 is added. [6] This will cause the gel to be blue when dry and pink when hydrated. [6] Due to a link between the cobalt chloride and cancer, it has been forbidden in Europe for use in ...
Anhydrous cobalt(II) chloride is blue, while the hexahydrate is magenta in colour. [1] Because the color change of cobalt(II) chloride in different hydrates, it can be used to manufacture color-changing silica gel. Anhydrous cobalt halides react with nitric oxide at 70~120 °C to generate [Co(NO) 2 X] 2 (X = Cl, Br or I).
The desiccant, usually an otherwise-inert solid such as silica gel, fills the space under the platform. Colour changing silica may be used to indicate when it should be refreshed. Indication gels typically change from blue to pink (if the indicator is cobalt(II) chloride) as they absorb moisture but other colours may be used.
Cobalt(II) chloride is an inorganic compound, a salt of cobalt and chlorine, with the formula CoCl 2.The compound forms several hydrates CoCl 2 ·n H 2 O, for n = 1, 2, 6, and 9. . Claims of the formation of tri- and tetrahydrates have not been confirmed
A colorful example is cobalt(II) chloride, which turns from blue to red upon hydration, and can therefore be used as a water indicator.. The notation "hydrated compound⋅n H 2 O", where n is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated.