Chemical Analysis of Salts: Anions and Cations
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Preliminary Test
| Color of the Salt | Colourless | Absence of Cu 2+, Fe 2+, etc |
| Odour of the Salt | Ammoniacal smell Vinegar smell | NH4 Acetate ion |
| Solubility | In water with no precipitate with Na2CO3 In dil HCl, soluble | NH4 No Group 1 cations |
| Salt is heated in a dry test tube | Colorless gas turns milky Reddish brown fumes Smell of ammonia Pleasant smell | Carbonate Nitrate ion NH4 Acetate ion |
| Flame Test | Pale green Brick red | Ba Ca |
| Ash Test | Blue ash | Al |
Systematic Analysis for Anions
| Dil HCl is added to a little of the salt | Brisk effervescence of a colorless gas | CO3 |
| Salt is rubbed with dil H2SO4 in a watch glass | Vinegar smell | Acetate |
| Salt is heated with conc H2SO4 | Colorless pungent smelling gas is evolved and dense white fumes are produced when a glass rod dipped in NH4OH is shown near the mouth of the test tube | Chloride |
| Salt is heated with conc. H2S4 | Reddish brown vapors | Nitrate |
| Salt is acidified with dil HCl and BaCl2 | White ppt | Sulphate |
Systematic Analysis for Cations
| To aq salt soln, sodium carbonate sol is added | No ppt | Ammonium |
| Dil HCl is added to a little of the salt solution | White ppt | Lead |
| Solid NH4Cl added to salt solution of NH4OH | White gelatinous ppt | Al |
| Solid NH4Cl is added to salt and then NH4OH and (NH4)2CO3 added | White ppt | Ba or Ca |
Confirmatory Test for Anion
Carbonate | |
|---|---|
The above gas is passed through lime water | Lime water turns milky |
Few drops of BaCl2 solution is added | White ppt |
Chloride | |
|---|---|
Acidified with dil HNO3 and drops of silver nitrate | White ppt soluble in NH4OH |
Salt is heated with manganese dioxide and conc sulphuric acid | Greenish yellow gas |
Acetate | |
|---|---|
Salt is warmed with conc H2SO4 and ethyl alcohol then poured excess water taken in beaker | Fruity smell |
To salt soln, neutral ferric chloride solution is added | Red color formed |
Nitrate | |
|---|---|
Freshly prepared ferrous sulphate soln is added to a little of the salt soln and then conc. H2SO4 is added along the sides of the test tube | Brown ring is formed at the junction of the solution |
Salt solution acetic acid and lead acetate are added | Blue coloration |
| Sulphate | |
|---|---|
| Ti salt soln acetic acid and lead acetate soln are added | White ppt |
| Excess ammonium actate soln is added to the above ppt | Ppt is dissolved |
Confirmatory for Cations
| Ammonium ion | |
|---|---|
| To salt soln NaOH soln is added and then Nessler's reagent | Reddish brown ppt |
| Salt soln is heated with NaOH soln | Smell of ammonia and dense white fumes are produced when a glass rod is brought near the mouth of the test tube |
| Aluminum | |
|---|---|
| Group III ppt is dissolved in dil HCl and added 2 drops of litmus soln. To this added NH4OH drop wise | Blue ppt floating the colorless solution |
| Salt is dissolved in 2 drops of conc HNO3 and boiled with a few drops of cobalt nitrate soln. A filter paper soaked in this soln is burnt to ashes | Blue ash |
| Barium | |
|---|---|
| A little acetic acid and potassium chromate solution are added to a little of salt soln | Yellow ppt |
| Flame test | Pale green color is imparted to the flame |
| Calcium | |
|---|---|
| To salt soln ammonium chloride, NH4 hydroxide and NH4 oxalate solutions are added | White crystalline ppt |
| Flame test | Brick red color is imparted to the flame |