Salt Analysis2

Salt Analysis Step 1: Note Colour of Salt Colour of Salt Blue or Bluish Green Green Light Green Light Pink Dark Brown Yellow White

Inference Cu2+ or Ni2+ Ni2+ Fe2+ Mn2+ Fe3+ Fe3+ or ferrous carbonate All above mentioned cations are absent

Step 2: Smell the salt. Rub a little of the given salt between your fingers and smell. Smell Smell of vinegar Ammoniacal Smell Smell like rotten eggs

Inference CH3COONH4+ S-

Step 3: Flame test. Make a paste of salt with concentrated HCl and introduce small quantity into oxidising flame. Colour of Flame Inference Brick red Ca2+ Crimson red Sr2+ Light Green (appears after sometime) Ba2+ Bluish Green Cu2+ Step 4: Solubility test. Original Solution Cold distilled water Hot distilled water Cold dilute HCl Hot dilute HCl Cold concentrated HCl Hot concentrated HCl

Step 5 (If salt doesn’t dissolve in distilled water): Make sodium extract (S.E). Steps to prepare sodium extract: 1. Add 1 portion of salt to beaker. 2. Add 3 portions of Na2CO3.

3. Add 10-15 ml of water 4. Boil the mixture for 5 minutes 5. Cool the mixture. 6. Filter the mixture.

7. Use residue for the experiment. Step 6: Test for ammonia. Test for Ammonia Boil the O.S and pass effervescence through nessler’s reagent. Heat a small quantity of salt with NaOH solution.

Inference Nessler’s reagent turns orange. Ammoniacal smell.

Step 7: Dilute H2SO4 test for anions. Add salt to dilute H2SO4 and heat and pass effervescence through Lime Water Lead acetate paper (gas evolved smells of rotten eggs) Acidified Potassium dichromate paper FeSO4 solution

Lime water turns milky Lead Acetate paper turns black

CO32S2-

Potassium dichromate paper turns green FeSO4 solution turns black

SO32-

Anion CO32-

Confirmatory Test Shake salt with water and filter. • Filtrate + dil. HCl • Filtrate + MgSO4

Result

(Soluble CO32-)

NO2-

• •

CO2 with effervescence White precipitate.

(Insoluble CO32-) S2SO32NO2-

Residue + dil. HCl W.E or S.E + acetic acid (3 drops) + Lead acetate solution W.E or S.E + BaCl2 solution W.E + acetic acid (2 drops) + FeSO4

CO2 with effervescence. Black precipitate White precipitate formed which dissolves in excess in dil. HCl Dark red colour

Step 8: Concentrated H2SO4 test for anions. Add salt to concentrated H2SO4 and pass effervescence through AgNO3 solution

White precipitate formed in AgNO3 solution Starch paper Starch paper turns yellow or orange Starch paper turns blue FeSO4 solution FeSO4 solution turns black If none of the above tests are positive test for SO42Anion ClBrINO3-

CH3COOSO42-

Confirmatory Test S.E + dil. HNO3. Boil and add AgNO3 solution. S.E + dil. HNO3. Boil and add AgNO3 solution. S.E + dil. HNO3. Boil and add AgNO3 solution. Salt + conc. H2SO4 +Cu chips. Heat. W.E + FeSO4 + conc. H2SO4 by sides of test tube. W.E + neutral FeCl3 solution W.E or S.E + dil. HCl + BaCl2 solution

ClBrINO3and acetate Result White precipitate soluble in NH4OH. Pale yellow precipitate which is partially soluble in NH4OH. Yellow precipitate insoluble in NH4OH. Reddish brown vapours. Brown ring formed. Blood red colour. White precipitate formed which is insoluble in dil. HCl

Step 9: Test for Cations. (Check confirmation table if a group precipitates) Experiment Group 1:To O.S add dilute HCl. Group 2: Acidify O.S with dilute HCl and pass H2S gas through it. Group 3: Boil of H2S gas completely and then add I gm of NH4Cl and 0.5 cm3 of conc. HNO3. Boil and cool and then add NH4OH till it smells of ammonia.

Observation White precipitate if formed Black precipitate is formed

Inference Pb2+, Ag+

•

• • • •

Fe3+ Al3+ Cr3+ Fe2+

Group 4: Pass H2S gas through solution of group 3 or O.S + NH4OH+ H2S gas Group 5: Take Filtrate of group 4. Boil of H2S and divide solution into three parts. Add NH4Cl, NH4OH and (NH4)2CO3. Filter. Group 6: To filtrate add a pinch of NH4OH and excess of ammonium phosphate solution.

• • •

• • •

Zn2+ Ni2+ Mn2+

• • •

Reddish brown precipitate White precipitate Green precipitate For Fe2+: O.S or filtrate of group 2 + Potassium ferricyanide solution. White precipitate Black precipitate Flesh coloured precipitate

Pb2+, Cu2+

White precipitate

Ba2+, Sr2+ or Ca2+

White precipitate

Mg2+

Confirmatory Test Boil the white precipitate with distilled water and divide solution into two parts • To one part add KI solution • To second part add K2CrO4 solution Dissolve black

Result • Yellow precipitate • Yellow precipitate

Confirmation Table: Cation Pb2+

Cu2+

•

Deep blue solution

Fe3+

Fe2+ Al3+

Zn2+

Ca2+, Sr2+ and Ba2+

precipitate in 50% HNO3. Bluish green solution formed. • Add excess of NH4OH solution to bluish green solution. • Acidify bluish green solution with acetic acid and add potassium ferrocyanide solution. Dissolve brown precipitate in dilute HCl and divide into two parts. • To first part add potassium ferrocyanide solution • To second part add potassium sulphocyanide solution. O.S + Potassium ferricyanide solution White precipitate + dil. HCl + few drops of blue litmus solution + NH4OH solution in excess Dissolve part of white precipitate in dil. HCl. Divide solution into two parts. • To one part add potassium ferrocyanide solution • To second part add NaOH solution Dissolve white precipitate in dil. Acetic acid. Boil of CO2. • To one part K2Cr04 solution. • To second part add ammonium sulphate

•

Chocolate brown precipitate.

•

Prussion blue colour or precipitate Blood red colouration.

•

A blue colour or precipitate A blue precipitate suspended in a colourless liquid • •

• • •

Bluish white precipitate White precipitate soluble in excess of NaOH

Yellow precipitate confirms Ba2+. White precipitate confirms Sr2+. White precipitate confirms Ca2+.

Mg2+

solution. • To third part add ammonium oxalate solution. Wash and suspend a part of white precipitate in water. Add a drop of HCl followed by a few drops of magneson reagent and excess of NaOH solution

Blue precipitate or colouration.