The chromium chloride (CrCl3) is an inorganic salt composed of Cr cations3+ and Cl anions- in a 1: 3 ratio; that is, for each Cr3+ there are three Cl-. As will be seen later, their interactions are not ionic. This salt can be presented in two forms: anhydrous and hexahydrated..
The anhydrous form is characterized by a reddish-violet color; while the hexahydrate, CrCl3.6HtwoOr, it's dark green. The incorporation of the water molecules modifies the physical properties of said crystals; such as their boiling and melting points, densities, etc..
Chromium (III) chloride (according to the stock nomenclature) decomposes at high temperatures, transforming into chromium (II) chloride, CrCltwo. It is corrosive to metals, although it is used in chrome plating: a procedure in which metals are coated with a thin layer of chromium.
The cr3+, coming from its respective chloride, it has been used in the treatment of diabetes, especially in patients with total parenteral nutrition (TPN), who do not ingest the required amount of chromium. However, the results are much better (and more reliable) if supplied as picolinate..
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The CrCl3 Despite being a salt, the nature of its interactions are not purely ionic; have a certain covalent character, product of the coordination between Cr3+ and Cl-, which give rise to a deformed octahedron (upper image). Chromium is located in the center of the octahedron, and chlorines in its vertices.
The octahedron CrCl6 may, at first glance, contradict the CrCl formula3; however, this complete octahedron does not define the unit cell of the crystal, but rather a cube (also deformed), which cuts the green spheres or chlorine anions in half.
Thus, the unit cell with this octahedron still maintains the 1: 3 ratio. By reproducing these deformed cubes in space, the CrCl crystal is obtained3, which is represented in the upper image with a three-dimensional filling model, and a model of spheres and bars.
This crystalline layer is one of the many that make up the flaky reddish-violet crystals of CrCl.3 (do not confuse the color of the crystal, true, with that of the green spheres).
As can be seen, the anions Cl- they occupy the surface, so their negative charges repel the other crystalline layers. Consequently, the crystals become flaky and brittle; but shiny, because of the chrome.
If these same layers are visualized from a lateral perspective, it will be observed, instead of octahedra, distorted tetrahedra:
Here it is further facilitated the understanding of why the layers repel each other when Cl anions bind.- of their surfaces.
-Chromium (III) chloride
-Chromium (III) trichloride
-Chromium (III) chloride anhydrous.
-CrCl3 (anhydrous).
-CrCl3.6HtwoO (hexahydrate).
-158.36 g / mol (anhydrous).
-266.43 g / mol (hexahydrate).
-Reddish-violet solids and crystals (anhydrous).
-Dark green crystalline powder (hexahydrate, bottom image). In this hydrate it can be seen how water inhibits shine, a metallic characteristic of chromium.
-1,152 ºC (2,106 ºF, 1,425 K) (anhydrous)
-83 ºC (hexahydrate).
1300ºC (2,370ºF, 1,570) (anhydrous).
-Slightly soluble (anhydrous).
-585 g / L (hexahydrate).
The image above shows a series of test tubes filled with an aqueous solution of CrCl3. Note that the more concentrated it is, the more intense the color of the complex [Cr (OHtwo)6]3+, responsible for the green color.
Soluble in ethanol, but insoluble in ether (anhydrous).
-2.87 gr / cm3 (anhydrous).
-2.76 g / cm3 (hexahydrate).
When heated to decomposition, chromium (III) chloride emits toxic fumes of chlorine-containing compounds. These compounds are also released when chromium (III) chloride comes into contact with strong acids..
It is highly corrosive and can attack certain steels.
It is incompatible with strong oxidants. It also reacts strongly with lithium and nitrogen..
When heated in the presence of hydrogen, it reduces to chromium (II) chloride, with the formation of hydrogen chloride.
2 CrCl3 + Htwo => 2 CrCltwo + 2 HCl
In an aqueous solution, and with a concentration of 0.2 M: 2.4.
Chromium (III) chloride hexahydrate is produced by reacting chromium hydroxide with hydrochloric acid and water.
Cr (OH)3 + 3 HCl + 3 HtwoO => CrCl3.6HtwoOR
Then, to obtain the anhydrous salt, the CrCl is heated3.6HtwoOr in the presence of thionyl chloride, SOCltwo, hydrochloric acid, and heat:
[Cr (HtwoOR)6] Cl3 + 6SOCltwo + ∆ → CrCl3 + 12 HCl + 6SOtwo
Alternatively, CrCl3 obtained by passing chlorine gas over a mixture of chromium and carbon oxide.
CrtwoOR3 + 3 C + Cltwo => 2 CrCl3 + 3 CO
And finally, being the most used method, it is to heat its oxide with a halogenating agent, such as carbon tetrachloride:
CrtwoOR3 + 3CCl4 + ∆ → 2CrCl3 + 3COCltwo
Chromium chloride is involved in the in situ preparation of chromium (II) chloride; reagent involved in the reduction of alkyl halides, and in the synthesis of (E) -alkenyl halides.
-It is used in the chrome plating technique. This consists of depositing, by means of electroplating, a thin layer of chromium on metal objects or other material with a decorative objective, thus increasing the resistance to corrosion and also the surface hardness..
-It is used as a textile mordant, serving as a link between the dyeing material and the fabrics to be dyed. In addition, it is used as a catalyst for the production of olefins and waterproofing agents..
The use of chromium chloride supplement USP is recommended in patients who only receive intravenous solutions, administered for total parenteral nutrition (TPN). Therefore, only when these patients do not receive all their nutritional requirements.
Chromium (III) is part of the glucose tolerance factor, an activator of insulin-promoting reactions. Chromium (III) is thought to activate glucose, protein and lipid metabolism, facilitating the action of insulin in humans and animals.
Chromium is present in many foods. But its concentration does not exceed 2 per serving, broccoli being the food with the highest contribution (11 µg). Additionally, the intestinal absorption of chromium is low, with a value of 0.4 to 2.5% of the amount ingested..
This makes it difficult to establish a diet for the supply of chromium. In 1989, The National Academy of Sciences recommended 50 to 200 µg / day as an adequate intake of chromium..
Among the possible risks of consuming this salt as a chromium supplement are:
-Severe stomach pains.
-Abnormal bleeding, which can range from difficulty healing a wound, redder bruising, or darkening of the stool from internal bleeding.
-Irritations in the digestive system, causing ulcers in the stomach or intestines.
-Dermatitis
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