Just add Water to Hydroxide.
Many British people thinking back to their schooldays will remember seeing the burning ofmagnesium ribbon, possibly even doing the experiment themselves. You may recall the instruction of your teacher to ‘look away’ or ‘not to stare at the bright light’ or ‘put your hands over your eyes’. Then the piece of magnesium would be lowered into the Bunsen flame, and would soon ignite. You’d be looking away by now, but would be conscious of a blinding white light – which is why magnesium is used in signal flares...
Being a metal oxide, magnesium oxide is basic. You can demonstrate this easily if you just shake some powdered magnesium oxide with water for a while. Magnesium oxide is only very slightly soluble in water – so it won’t be obvious that a small amount has dissolved – but if you now test the liquid with an indicator, it will give an alkaline reaction, showing that at least some Mg(OH)2, magnesium hydroxide, has been formed.
For this reason, magnesium oxide is used to treat heartburn and effects of acid stomach, as it neutralises excess acid. These properties have been used medicinally for a couple of centuries. Many of you will recognise the blue glass bottles bearing the label ‘milk of magnesia’, which is a suspension of magnesium hydroxide in water, with a bit of added peppermint. Apart from treating the effects of excess acid, milk of magnesia is also a laxative.