antacid

[kyle32123]

i have a bottle of antacid with Aluminum hydroxide and magnesium hydroxide, i wanna try to extract the aluminum hydroxide from the antacid, if it is even possible to do, it had other inacive ingredients in the antacid, any ideas on how this can be done?

[woelen]

If you only have magnesium hydroxide and aluminium hydroxide in the stuff, then you can proceed as follows:

 

Add excess solution of NaOH. The aluminium hydroxide will dissolve as sodium aliminate (it is amphoteric), while the magnesium hydroxide remains a solid. Let the solid settle and decant the clear liquid from the solid.

 

To the clear liquid, you carefully have to add an acid, such that aluminium hydroxide is formed again. If you add too much acid, then the aluminium hydroxide will dissolve again.

 

This procedure, however, by no means is easy and your end-product most likely will contain a lot of impurities, being sodium ions and the anion of the acid, used to convert the aluminate to aluminium hydroxide. Also from a practical point of view, it will not be easy. The precipitates involved are very slimy and flocculent and do not easily form nice compact layers on the bottom . If you have a centrifuge, then things will become easier. Using a fine filter also will be an option, but the slimyness easily clogs the pores of the filter and then filtering become VERY slow, unless you have a vacuumpump.