Editing Qualitative inorganic analysis (section)

=== 1st analytical group of anions ===
The ''1st group of anions'' consist of [[Carbonate|CO{{su|b=3|p=2&minus;}}]], [[Bicarbonate|HCO{{su|b=3|p=&minus;}}]], [[Acetate|CH<sub>3</sub>COO<sup>&minus;</sup>]], [[Sulfide|S<sup>2&minus;</sup>]], [[Sulfite|SO{{su|b=3|p=2&minus;}}]], [[Thiosulfate|{{chem|S|2|O}}{{su|b=3|p=2&minus;}}]] and [[Nitrite|NO{{su|b=2|p=&minus;}}]]. The reagent for Group 1 anions is dilute hydrochloric acid (HCl) or dilute sulfuric acid (H<sub>2</sub>SO<sub>4</sub>).

* Carbonates give a brisk effervescence with dilute H<sub>2</sub>SO<sub>4</sub> due to the release of CO<sub>2</sub>, a colorless gas which turns [[limewater]] milky due to formation of CaCO<sub>3</sub> ([[carbonatation]]). The milkiness disappears on passing an excess of the gas through the lime water, due to formation of Ca(HCO<sub>3</sub>)<sub>2</sub>.
* Acetates give the vinegar-like smell of CH<sub>3</sub>COOH when treated with dilute H<sub>2</sub>SO<sub>4</sub> and heated. A blood red colouration is produced upon addition of yellow FeCl<sub>3</sub>, due to formation of [[iron(III) acetate]].
* Sulfides give the rotten egg smell of H<sub>2</sub>S when treated with dilute H<sub>2</sub>SO<sub>4</sub>. The presence of sulfide is confirmed by adding [[lead(II) acetate]] paper, which turns black due to the formation of PbS. Sulfides also turn solutions of red [[sodium nitroprusside]] purple.
* Sulfites produce SO<sub>2</sub> gas, which smells of burning sulfur, when treated with dilute acid. They turn acidified K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> from orange to green.
* Thiosulfates produce SO<sub>2</sub> gas when treated with dilute acid. In addition, they form a cloudy precipitate of [[sulfur]].
* Nitrites give reddish-brown fumes of NO<sub>2</sub> when treated with dilute H<sub>2</sub>SO<sub>4</sub>. These fumes cause a solution of [[potassium iodide]] (KI) and [[starch]] to turn blue.