Editing Qualitative inorganic analysis (section)

=== 6th analytical group of cations ===
Cations which are left after carefully separating previous groups are considered to be in the sixth analytical group. The most important ones are [[magnesium|Mg<sup>2+</sup>]], [[lithium|Li<sup>+</sup>]], [[Sodium|Na<sup>+</sup>]] and [[potassium|K<sup>+</sup>]]. All the ions are distinguished by flame color: lithium gives a red flame, sodium gives bright yellow (even in trace amounts), potassium gives violet, and magnesium, colorless (although magnesium metal burns with a bright white flame). Magnesium can also be distinguished from other cations in this group by adding sodium hydroxide to drive the pH to 11 or higher, which selectively precipitates Mg(OH)<sub>2</sub>.