Magnesium is precipitated from its salt solution as only magnesium ammonium phosphate by adding disodium hydrogen phosphate solution in absence of ammonium chloride and aqueous ammonia.

Explanation

To solve the problem of precipitating magnesium from its salt solution as magnesium ammonium phosphate, we can follow these steps:

### Step 1: Identify the Reactants
We start with a magnesium salt solution, such as magnesium chloride (MgCl₂), and we will add disodium hydrogen phosphate (Na₂HPO₄) to it. We will not add ammonium chloride (NH₄Cl) or aqueous ammonia (NH₃) in this process.

### Step 2: Write the Reaction
When we add disodium hydrogen phosphate to the magnesium salt solution, the following reaction occurs:

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