He magnesium phosphate is a term used to refer to a family of inorganic compounds formed by magnesium, alkaline earth metal and oxoanion phosphate. The simplest magnesium phosphate has by chemical formula Mg 3 (PO 4 ) 2 . The formula indicates that for every two PO anions 4 3- there are three Mg cations 2+ interacting with these.
Also, these compounds can be described as magnesium salts derived from orthophosphoric acid (H 3 PO 4 ). In other words, magnesium"cools"between phosphate anions, regardless of their inorganic or organic presentation (MgO, Mg (NO 3 ) 2 , MgCl 2 , Mg (OH) 2 , etc.).
Due to these reasons, magnesium phosphates can be found as several minerals. Some of these are: catheita -Mg 3 (PO 4 ) 2 · 22H 2 O-, struvite - (NH 4 ) MgPO 4 · 6H 2 Or, whose microcrystals are represented in the top image-, holtedalite -Mg 2 (PO 4 ) (OH) - and bobierrita -Mg 3 (PO 4 ) 2 · 8H 2 OR-.
In the case of the bobierrita, its crystalline structure is monoclinic, with crystalline aggregates with fan shapes and massive rosettes. However, magnesium phosphates are characterized by exhibiting a rich structural chemistry, meaning that their ions adopt many crystal arrangements.
Index
- 1 Forms of magnesium phosphate and the neutrality of its charges
- 1.1 Magnesium phosphates with other cations
- 2 Structure
- 3 Properties
- 4 Applications
- 5 References
Forms of magnesium phosphate and the neutrality of its charges
Magnesium phosphates are derived from the substitution of H protons 3 PO 4 . When the orthophosphoric acid loses a proton, it remains as the dihydrogen phosphate ion, H 2 PO 4 - .
How to neutralize the negative charge to originate a magnesium salt? Yes Mg 2+ account for two positive charges, then you need two H 2 PO 4 - . Thus, magnesium diacid phosphate, Mg (H) is obtained 2 PO 4 ) 2 .
Next, when the acid loses two protons, the hydrogen phosphate ion remains, HPO 4 2- . Now, how to neutralize these two negative charges? Like the Mg 2+ it only needs two negative charges to neutralize, interacts with a single HPO ion 4 2- . In this way the magnesium acid phosphate is obtained: MgHPO 4 .
Finally, when all protons are lost, phosphate anion PO remains 4 3- . This requires three Mg cations 2+ and another phosphate to assemble into a crystalline solid. Mathematical equation 2 (-3) + 3 (+2) = 0 helps understand these stoichiometric ratios for magnesium and phosphate.
As a result of these interactions, the tribasic magnesium phosphate is produced: Mg 3 (PO 4 ) 2 . Why is it tribasic? Because it is capable of accepting three equivalents of H + to form the H again 3 PO 4
PO 4 3- (ac) + 3H + (ac) H 3 PO 4 (ac)
Magnesium phosphates with other cations
The compensation of negative charges can also be achieved with the participation of other positive species. For example, to neutralize the PO 4 3- , the K ions + , Na + , Rb + , NH 4 + , etc., can also intercede, forming the compound (X) MgPO 4 . If X equals NH 4 + , the anhydrous struvite mineral is formed, (NH 4 ) MgPO 4 .
Given the situation that another phosphate intervenes and the negative charges increase, other additional cations can be added to the interactions to neutralize them. Thanks to this, numerous magnesium phosphate crystals can be synthesized (Na 3 RbMg 7 (PO 4 ) 6 , for example).
Structure
The upper image illustrates the interactions between Mg ions 2+ and PO 4 3- that define the crystalline structure. However, it is only an image that demonstrates rather the tetrahedral geometry of the phosphates. Then, the crystal structure involves tetrahedra of phosphates and magnesium spheres.
For the case of Mg 3 (PO 4 ) 2 Anhydrous, the ions adopt a rhombohedral structure, in which Mg 2+ is coordinated with six atoms of O. The above is illustrated in the lower image, with the notation that the blue spheres are cobalt, it is enough to change them for the green magnesium spheres:
Right in the center of the structure can be located the octahedron formed by the six red spheres around the bluish sphere.
Also, these crystalline structures are capable of accepting water molecules, forming magnesium phosphate hydrates. This is because they form hydrogen bonds with phosphate ions (HOH-O-PO 3 3- ). In addition, each phosphate ion is capable of accepting up to four hydrogen bonds; that is, four water molecules.
Like the Mg 3 (PO 4 ) 2 has two phosphates, can accept eight water molecules (what happens with the mineral bobierrita). In turn, these water molecules can form hydrogen bonds with others or interact with positive Mg centers 2+ .
Properties
It is a white solid, forming crystalline rhombic plates. Also, it has no smell and no flavor.
It is very insoluble in water, even when it is hot, due to its great crystal lattice energy; this is a product of the strong electrostatic interactions between the polyvalent Mg ions 2+ and PO 4 3- . That is, when the ions are polyvalent and their ionic radii do not vary much in size, the solid shows resistance to its dissolution.
It melts at 1184 ° C, which is also indicative of strong electrostatic interactions. These properties vary depending on how many water molecules are absorbed, and whether the phosphate is in some of its protonated forms (HPO) 4 2- or H 2 PO 4 - ).
Applications
It has been used as a laxative for states of constipation and gastric acidity. However, its harmful side effects - manifested by the generation of diarrhea and vomiting - have limited its uses. In addition, it is likely to cause damage to the gastrointestinal tract.
The use of magnesium phosphate in the repair of bone tissue is currently being explored, investigating the application of Mg (H) 2 PO 4 ) 2 as cement.
This form of magnesium phosphate meets the requirements for this: it is biodegradable and histocompatible. In addition, its use in the regeneration of bone tissue is recommended for its strength and fast setting.
The use of amorphous magnesium phosphate (AMP) as a biodegradable and non-exothermic orthopedic cement is being evaluated. To generate this cement, the AMP powder is mixed with polyvinyl alcohol, in order to form a putty.
The main function of magnesium phosphate is to provide Mg's contribution to living beings. This element intervenes in numerous enzymatic reactions as a catalyst or intermediary, being essential for life.
A deficiency of Mg in humans is associated with the following effects: decreased Ca levels, heart failure, Na retention, decreased K levels, arrhythmias, sustained muscle contractions, vomiting, nausea, low circulating levels of parathyroid hormone and stomach and menstrual cramps, among others.
References
- SuSanA Secretariat. (December 17, 2010). Struvite under the microscope. Retrieved on April 17, 2018, from: flickr.com
- Mineral Data Publishing. (2001-2005). Bobierrite. Retrieved on April 17, 2018, from: handbookofmineralogy.org
- Ying Yu, Chao Xu, Honglian Dai; Preparation and characterization of a degradable magnesium phosphate bone cement, Regenerative Biomaterials , Volume 3, Issue 4, 1 December 2016, Pages 231-237, doi.org
- Sahar Mousa. (2010). Study on synthesis of magnesium phosphate materials. Phosphorus research bulletin Vol. 24, pp. 16-21.
- Smokefoot. (March 28, 2018). EntryWithCollCode38260. [Figure]. Retrieved on April 17, 2018, from: commons.wikimedia.org
- Wikipedia. (2018). Magnesium phosphate tribasic. Retrieved on April 17, 2018, from: en.wikipedia.org
- Pubchem. (2018). Magnesium Phosphate Anhydrous. Retrieved on April 17, 2018, from: pubchem.ncbi.nlm.nih.gov
- Ben Hamed, T., Boukhris, A., Badri, A., & Ben Amara, M. (2017). Synthesis and crystal structure of a new magnesium phosphate Na3RbMg7 (PO4) 6. Acta Crystallographica Section E: Crystallographic Communications, 73 (Pt 6), 817-820. doi.org
- Barbie, E., Lin, B., Goel, V.K. and Bhaduri, S. (2016) Evaluation of amorphous magnesium phosphate (AMP) based non-exothermic orthopedic cement. Biomedical Mat. Volume 11 (5): 055010.
- Yu, Y., Yu, CH. and Dai, H. (2016). Preparation of a degradable magnesium bone cement. Regenerative Biomaterials. Volume 4 (1): 231