Question

How would one prepare magnesium citrate from magnesium chloride and citric acid? Will it work if I just heat a mixture of magnesium chloride and citric acid in water? I'd expect HCl to vaporize off.

Does anyone have experience with this reaction? Yield, purity, concentrations, byproducts, ... So if I just try to make magnesium citrate directly by mixing the chloride and citric acid, will that work – or is the citrate going to degrade/decompose into organic byproducts?

Background

I have a large amount of high purity magnesium chloride on hand which is slowly deliquescing anyway. I'd like to convert it into magnesium citrate (molar ratio of magnesium to citrate isn't hugely important, aim between 1 and 1.5) which is easier to store – and I need it anyways (need magnesium solution chelated with citrate and bitartrate).

I figure I could buy citric acid food grade, which is cheap enough, to make magnesium citrate. Objective is to have a high yield, low energy usage if possible (not having to boil off loads and loads of water, not having many steps), and no byproducts / few and easy purification steps necessary (a high grade end result consisting of only citrate and magnesium).

Economic feasibility (answer)

Magnesium chloride hexahydrate costs about 2.5 €/mol and sodium carbonate 1.1 €/mol. The product, magnesium carbonate is worth about 2.6 €/mol. So converting to carbonate results in a loss.
Citric acid monohydrate costs about 2.6 €/mol. The product, magnesium citrate is worth about 12.3 €/mol. So this step is profitable (gain 12.3 at a cost of 2.6+2.6).
Converting magnesium chloride into its citrate directly (if it were at all possible) would be profitable (gain 12.3 at a cost of 2.6+2.5).

Answer 1

To prepare magnesium citrate from magnesium chloride and citric acid, dissolve them in water, and remove formed HCl. However, heating may lead to decomposition, requiring careful pH control to achieve desired yield and purity.

To prepare magnesium citrate from magnesium chloride and citric acid, you would first dissolve both compounds in water to create a solution. When magnesium chloride (
`MgCl_2`) is mixed with citric acid (
`C_(6)H_(8)O_7`), the chloride ions would potentially react with H+ from the citric acid to form HCl, which could then be removed by evaporation or distillation given its lower boiling point compared to water.

However, heating a mixture may not be the most efficient way to generate a high yield of pure magnesium citrate, as the citrate could decompose under heat or certain pH conditions. The direct reaction may require careful pH control and consideration of water content.

Considering economic feasibility, direct conversion of magnesium chloride to magnesium citrate may be profitable, given that the cost of producing magnesium citrate is outweighed by its market value. However, in practice, achieving the desired yield and purity might necessitate further purification steps to remove any byproducts or unreacted starting materials.