Mag Phos: How Magnesium Hydrogen Phosphate Trihydrate Is Made
At a glance
|
Chemical name |
Magnesium hydrogen phosphate trihydrate |
|
Alternative name |
Dibasic magnesium phosphate trihydrate |
|
Chemical formula |
MgHPO₄·3H₂O |
|
Water solubility |
Slightly soluble |
|
Natural mineral |
Newberyite, a rare mineral |
Magnesium phosphate minerals are relatively uncommon. The specific compound used for Mag Phos, MgHPO₄·3H₂O, occurs naturally as newberyite, but the mineral is too rare to serve as the usual commercial source of pharmaceutical-grade material.
Manufacturers therefore obtain magnesium from abundant minerals or brines and phosphate from phosphate rock, purify the two components separately, and then crystallize magnesium hydrogen phosphate trihydrate under controlled conditions.
|
Body connection: Magnesium helps enzymes use ATP Magnesium is required for the activity of hundreds of enzymes. ATP, or adenosine triphosphate, has the molecular formula C₁₀H₁₆N₅O₁₃P₃ and supplies energy for processes such as muscle contraction, nerve signalling, and protein synthesis. Inside cells, ATP’s phosphate groups carry negative charges, and a positively charged magnesium ion, Mg²⁺, binds near their oxygen atoms to form Mg–ATP. For many enzymes, this magnesium complex is the usable form of ATP. |
Preparing a purified magnesium source
Magnesium may begin in magnesite (MgCO₃), dolomite (CaMg(CO₃)₂), magnesium oxide (MgO), or magnesium-rich brines. After separation and purification, the magnesium is converted into a soluble compound suitable for controlled reaction chemistry.
For example, magnesium carbonate can be reacted with hydrochloric acid:
|
MgCO₃ + 2HCl → MgCl₂ + CO₂ + H₂O |
Magnesium oxide may also be converted to magnesium chloride:
|
MgO + 2HCl → MgCl₂ + H₂O |
The resulting MgCl₂ solution provides a purified, measurable source of Mg²⁺ ions. Other purified magnesium compounds may be used depending on the manufacturer’s process.
Preparing the phosphate source
The phosphate component is obtained from purified phosphate material derived from apatite-rich rock, commonly in the form of phosphoric acid, H₃PO₄ (see Calc Phos for more details).
Forming the trihydrate
One simplified route reacts magnesium hydroxide with phosphoric acid in the presence of sufficient water to form the trihydrate:
|
Mg(OH)₂ + H₃PO₄ + H₂O → MgHPO₄·3H₂O↓ |
Magnesium hydrogen phosphate is only slightly soluble, so it crystallizes from the reaction mixture. During crystallization, three water molecules become incorporated into each MgHPO₄ unit and become part of the crystal lattice.
This hydrate formation must be controlled carefully. Temperature, pH, concentration, mixing, addition rate, reaction time, and the magnesium-to-phosphate ratio influence which magnesium phosphate compound forms, its hydration state, and its crystal size and morphology.
Separation, drying, and testing
The crystals are separated and washed to remove soluble by-products and excess starting materials. Controlled drying removes surface moisture while preserving the three structural water molecules required by the formula MgHPO₄·3H₂O.
The material may be milled and classified before testing for identity, magnesium and phosphate assay, moisture, hydration state, particle characteristics, residual salts, heavy metals, and other elemental impurities.