The cadmium hydroxide (Cd (OH) 2) is a substance of inorganic origin, characterized by being in the solid state in the form of white crystals. It is a substance of ionic nature with a hexagonal-type crystalline structure, constituting a hydroxide whose behavior is amphoteric.
In this sense, cadmium hydroxide can be produced in different ways, such as, for example, through the treatment of the salt known as cadmium nitrate with the strong base sodium hydroxide.
By Ondřej Mangl, from Wikimedia Commons
This hydroxide is used in numerous applications, including the process known as cadmium plating or plating, although it is also widely used in the preparation of other salts of this transition metal.
On the other hand, exposure to this compound can carry health risks, because it is absorbed through contact with the skin and through the respiratory tract. It should be noted that it is considered a carcinogenic substance.
Structure
Cadmium hydroxide is made up of only two ions: cadmium (Cd 2+) and hydroxyl (OH -), thus forming an ionic compound with the molecular formula Cd (OH) 2.
The structure of this compound is quite similar to that of magnesium hydroxide (Mg (OH) 2), since its crystals have a molecular arrangement that obeys a hexagonal symmetry, according to the unit cells that make them up.
In the same way, this substance can be produced by treating cadmium metal nitrate (Cd (NO 3) 2) with a certain amount of sodium hydroxide (NaOH), according to the following equation:
Cd (NO 3) 2 + 2NaOH → Cd (OH) 2 + 2NaNO 3
Although it exhibits similarities to zinc hydroxide, Cd (OH) 2 is considered to possess characteristics of greater basicity.
Also, since cadmium belongs to block d of the periodic table, it used to be considered a transition metal, so this and other similar metal hydroxides such as zinc are considered transition metal hydroxides.
In this class of chemical species, the largest oxoanion is the hydroxide, and the element with the highest molar mass or molecular weight that is not found in the oxoanion turns out to be one of the transition metals.
Properties
Among the most outstanding properties of cadmium hydroxide are:
-It is an ionic species belonging to inorganic compounds, whose structure is crystalline and has a hexagonal arrangement.
-Its molecular formula is described as Cd (OH) 2 and its molecular weight or molar mass is approximately 146.43 g / mol.
-It has amphoteric behavior, that is, it can act as an acid or a base depending on the chemical reaction and the environment in which it is carried out.
-Its density is approximately 4.79 g / cm 3 and it is considered soluble in acidic substances of low concentration (diluted).
-It is capable of forming an anionic coordination compound when it is treated with a concentrated solution of sodium hydroxide.
-It can also form coordination compounds with ammonium, thiocyanate or cyanide ions when added to solutions containing these ionic species.
-It usually experiences dehydration (loss of water molecules) when it is subjected to heating, forming cadmium oxide (CdO).
-When heated, it can also undergo thermal decomposition, but this only occurs between 130 and 300 ° C.
-It has numerous applications, but among them its use as a fundamental component in storage batteries stands out.
-Exhibits appreciable solubility when in alkaline solutions.
Applications
Cadmium hydroxide is used in a large number of uses and applications, such as those mentioned below.
In the manufacture of devices known as storage batteries, this chemical compound is used as an indispensable anodic component in the process.
Similarly, this hydroxide is a critical species when cadmium coating technique is performed on certain materials.
Also in the preparation of certain cadmium salts, although the procedure is not as simple as it is with the production of hydroxide.
On the other hand, when the devices known as silver-cadmium (Ag-Cd) and nickel-cadmium (Ni-Cd) accumulators are discharged, this compound is generated, according to the reaction shown below:
Cd + 2NiO (OH) + 2H 2 O → Cd (OH) 2 + Ni (OH) 2
Then, when recharging occurs, this hydroxide is transformed into the metallic form of cadmium through an intermediate product that is dissolved, and in this way other products can be generated.
In more recent applications, this hydroxide has been used in the production of nano-sized cables with a one-dimensional structure to be examined as an alternative thin-film electrode in supercapacitors.
Risks
Direct exposure to cadmium hydroxide has certain associated risks, whether by oral route, inhalation or dermal contact; such as the generation of vomiting and diarrhea.
Regarding the effects of chronic inhalation of the vapors produced by it, there are certain pulmonary diseases such as emphysema and bronchitis, pulmonary edema or pneumonitis of chemical causes can even occur.
Another consequence of prolonged exposure to this substance is the accumulation of cadmium in certain organs such as the kidneys or the liver, causing injury and permanent damage, because this compound causes a greater quantity of molecular proteins to be excreted, which are of a natural nature. vital in the body.
Similarly, loss or decrease in bone density or cadmium poisoning can occur.
In addition to these effects, this molecule combines with the estrogen receptor and causes its activation, which can stimulate development in some classes of cancer cells.
Likewise, this chemical species causes other estrogenic repercussions, such as the incapacitation of the reproductive function in human beings and, as its structure has a great affinity with that of zinc, cadmium can interfere in some of its biological processes.
References
- Wikipedia. (sf). Cadmium hydroxide. Recovered from en.wikipedia.org
- Chang, R. (2007). Chemistry, Ninth edition. Mexico: McGraw-Hill
- Ravera, M. (2013). Cadmium in the Environment. Recovered from books.google.co.ve
- Garche, J., Dyer, CK and Moseley, PT (2013). Encyclopedia of Electrochemical Power Sources. Obtained from books.google.co.ve
- Collins, DH (2013). Batteries 2: Research and Development in Non-Mechanical Electrical Power Sources. Recovered from books.google.co.ve