Salt Analysis Chart

SEMI – MICRO QUALITATIVE ANALYSIS OF SIMPLE INORGANIC SALT _______________________________________________________________ CATIONS: Pb2+ ,Hg2+ ,Cu2+ ,Cd2+ , Ag+ , Fe2+ , Fe3+ , Al3+ , Zn2+ , Mn2+ , Co2+ , Sr2+ , Ba2+ , Mg2+ , NH4+ ANIONS: CO32- , S2- , SO32- , SO42- , NO2- , NO3- , Cl- , Br2- , PO43- , CH3COO-

_______________________________________________________________ PRELIMINARY TESTS 1. Note the state (amorphous or crystalline) and colour of salt. 2. Test the solubility of the salt in the following solutions: i. Water (cold and hot) ii. Dilute HCl (cold and hot) iii. Dilute HNO3 (cold and hot)

_______________________________________________________________ IDENTIFICATION OF ACID RADICALS (ANIONS) This part is the classified into three groups:

FIRST GROUP OF ACID RADICALS The acid radicals involved in this group are carbonate(CO32-), Sulphide(S2-), Sulphite(SO32-), Thiosulphate(S2O32-) and nitrate(NO2-). The group reagent is dilute hydrochloric acid. EXPERIMENT Salt + dil. HCl

OBSERVATION

INFERENCE 1st group of acid radicals is present.

Effervescence or evolution of gases (a) Colourless, odourless gas turns lime water milky

The acid radical may be CO32- or HCO3-

(b) Colourless with rotten eggs smell and turns lead acetate paper black.

Sulphide(S2-) is confirmed.

(c) Colourless gas with suffocating smell. Heat and pass the gas through acidified K2Cr2O7 solution. The solution turns green

SO32- is confirmed.

(d) Colourless gas with suffocating smell with a yellow ppt. of sulphur in the test tube. Heat and pass the gas through acidified K2Cr2O7 solution. The solution turns dark blackish green.

S2O32- is confirmed.

(e) Colourless gas followed by brown gas and it turns starch iodide paper blue.

NO2- is confirmed.

(f) Colourless gas with the smell of vinegar.

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The acid radical may be CH3COO-

Tests to distinguish between CO32- and HCO3EXPERIMENT Salt + water, boil and pass the gas through lime water

OBSERVATION

INFERENCE

(a) Lime water does not turn milky.

CO32- is confirmed.

(b) Lime water turns milky.

HCO3- is confirmed.

Confirmation test for Acetate EXPERIMENT

OBSERVATION

Salt solution + Neutral FeCl3 sol.

Appearance of blood red colour.

INFERENCE Acetate is confirmed

SECOND GROUP OF ACID RADICALS

The acid radicals involved in this group are Cl-, Br- and NO3- . The group reagent is concentrated sulphuric acid (H2SO4). EXPERIMENT

Salt + Concentrated H2SO4 and heat if necessary.

OBSERVATION

INFERENCE

Effervescence with colourless or coloured gases

2nd group Acid radical is present

(a) Colourless gas with a pungent smell and gives dense white fumes when a glass rod dipped in ammonium hydroxide (NH4OH) is exposed.

The Acid radical may be Cl-

(b) Brown gas and the solution is not blue.

The acid radical may be Br-

(c) Light brown gas and brown gas with pieces of copper turnings and the solution turns blue in the test tube.

The Acid radical may be NO3-

Confirmation test for Chloride EXPERIMENT (a) Chromyl – Chloride test: Salt + few K2Cr2O7 crystals + conc. H2SO4 and heat Pass the vapours through the test tube which contains NaOH solution. To this yellow solution, add dilute CH3COOH and lead acetate solution.

(b) Silver Nitrate test: Salt solution + AgNO3 solution + dilute HNO3

OBSERVATION

INFERENCE

Red vapours are obtained. The solution turns yellow.

Chloride is confirmed.

Yellow ppt. is formed

White ppt. is formed which is soluble in NH4OH.

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Chloride is confirmed.

Confirmation test for Bromide EXPERIMENT

OBSERVATION

INFERENCE

(a) Globule Test: Aqueous solution of salt + two drops of CCl4 + 1ml chlorine water and shake well.

An orange-red globule is obtained

Bromide is confirmed.

(b)Silver Nitrate test: Salt solution + AgNO3 solution + dilute HNO3

A pale yellow ppt. slightly soluble in NH4OH is obtained.

Bromide is confirmed.

Confirmation test for Nitrate EXPERIMENT

OBSERVATION

Brown ring test: Strong solution of the substance + 2 or 3 drops of conc. H2SO4, and cool. Add freshly prepared FeSO4 solution on the sides of the test tube.

A brown ring is formed at the junction of two liquids.

INFERENCE Nitrate is confirmed.

THIRD GROUP OF ACID RADICALS The basic radicals involved in this group are SO42- and PO43- .

EXPERIMENT

OBSERVATION

INFERENCE

Test for Sulphate: Aqueous solution of salt + dilute HCl + BaCl2 solution.

A white ppt. insoluble in dilute HCl is obtained

Sulphate (SO42-) is confirmed.

Ammonium – Molybdate Test: 2ml of soda extract 1 + dilute HNO3 + Ammonium Molybdate solution.

A canary yellow precipitate is obtained.

Phosphate (PO43-) is confirmed.

1

Soda extract to be prepared if the given salt is partially soluble in water.

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ANALYSIS OF BASIC RADICALS OR CATIONS This is classified into 6 groups. They are mentioned as below:

GROUP

RADICALS

I

Pb2+ ,Ag+ 2+

II

Pb

,Hg

2+

2+

,Cu

GROUP REAGENTS Dilute Hydrochloric acid(HCl) 2+

,Cd

Dilute HCl + H2S gas.

Al3+ ,Fe2+ , Fe3+

III

2+

IV

Zn

2+

,Mn

2+

,Co

NH4Cl(s) + NH4OH 2+

,Ni

NH4Cl(s) + NH4OH + H2S gas

Ca2+ ,Sr2+ ,Ba2+

V VI

Mg

2+

, NH4

NH4Cl(s) + NH4OH + (NH4) 2CO3

+

-Nil-

Preparation of Original solution: A suitable solvent is found for the salt as given in the preliminary test. A few drops are used as solution. Test for NH4+ Radicals: This test is carried out before starting the analysis for the basic radicals.

EXPERIMENT (a) Salt + NaOH solution and heat it. Expose a glass rod dipped in conc. HCl to the gas and moist red litmus paper. (b) Original solution + Nesseler’s reagent.

OBSERVATION

INFERENCE

Colourless gas with a pungent smell is obtained. Dense white fumes and moist red litmus paper turns blue

NH4+ may be present in the salt

Brown solution or ppt. is obtained

NH4+ is confirmed.

FIRST GROUP OF BASIC RADICALS The basic radicals of this group are Pb2+ & Ag+ .The group reagent is dilute HCl.

EXPERIMENT (1) Original solution + Dilute HCl Filter and add water to ppt. and heat

OBSERVATION

INFERENCE

White ppt. is formed.

May be Pb2+ & Ag+

(a) ppt. dissolves in hot water.

May be Pb2+

(b) ppt. is insoluble in water.

May be Ag+

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(a) A yellow ppt. is formed.

(2) Original solution + Potassium Chromate solution.

Pb2+ is confirmed.

(b) A brick red ppt. is formed.

(3) Original solution + KCl sol.

Ag+ is confirmed.

A yellow ppt. soluble in hot water, on cooling reappears as golden yellow spangles. The yellow ppt. is insoluble in hot water.

ppt. obtained + water and heat it.

Pb2+ is confirmed.

SECOND GROUP OF BASIC RADICALS The basic radicals of this group are Pb2+, Hg2+, Cu2+ and Cd2+.The group reagent is Dilute HCl + H2S gas.

EXPERIMENT Original solution + Dilute HCl + H2S gas.

OBSERVATION

INFERENCE

(a)A Black ppt. is observed.

May be Pb2+ Hg2+ & Cu2+

(b)A yellow ppt. is observed.

May be Cd2+

The identification of Pb2+, Hg2+, Cu2+ and Cd2+ are as follows:

EXPERIMENT (a) Original solution + Potassium Chromate.

A yellow ppt. is observed.

(b)Original solution + NH4OH

A bluish white ppt. soluble in excess of NH4OH is observed which gives rise to a deep blue solution.

(c) Original solution + dil. acetic acid + potassium Ferro cyanide sol. (d) Dissolve the black ppt. in aqua regia 2 + 1ml of distilled water, heat & add 2 drops of SnCl2 (e) Original solution + dilute acetic acid + H2S gas.

2

OBSERVATION

A chocolate red ppt. is observed.

INFERENCE Pb2+ is confirmed. May be Cu2+ Cu2+ is confirmed.

A white ppt. is observed which turns grey.

Hg2+ is confirmed.

A yellow ppt. is formed.

Cd2+ is confirmed.

Aqua regia is mixture of 3 drops of HCl + 1 drop of HNO3

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THIRD GROUP OF BASIC RADICALS The basic radicals of this group are Al3+, Fe2+ and Fe3+ .The group reagent is NH4Cl + NH4OH

EXPERIMENT (1) Original solution + NH4Cl(s) + NH4OH in excess

(2) Original solution + NaOH solution

OBSERVATION

INFERENCE

(a) A white gelatinous ppt. is obtained.

May be Al3+

(b) A dirty green ppt. is obtained

May be Fe2+

(c) A reddish brown ppt. is obtained

May be Fe3+

(a) White gelatinous ppt. soluble in excess of NaOH is obtained which gives a colourless sol.

The basic radical is Al3+

(b) Dirty green ppt. insoluble in excess of NaOH

The basic radical is Fe2+

(c) Reddish brown ppt. insoluble in excess of NaOH

The basic radical is Fe3+

(3) Clear solution of 2(a) + solid NH4Cl and heat

The white gelatinous ppt. reappears.

Al3+ is confirmed.

(4) Original solution + acidified KMnO4 solution which is added drop wise.

(a) The pink colour of KMnO4 is not discharged.

Fe3+ is confirmed.

FOURTH GROUP OF BASIC RADICALS The basic radicals of this group are Zn2+, Mn2+, Co2+ & Ni2+.The group reagent is NH4Cl + NH4OH And H2S(g). EXPERIMENT (1) Original solution + NH4Cl(s) + NH4OH in excess + H2S(g)

(2) Original solution + NaOH solution+.

OBSERVATION (a) a white ppt. is obtained (b) Buff or pale pink or flash coloured ppt. soluble in dilute HCl is obtained.

INFERENCE May be Zn2+, Mn2+ or Co2+ May be Mn2+

(a) The white ppt. is soluble in excess of NaOH giving a colourless solution.

Zn2+ is confirmed

(b) The white ppt. insoluble in excess of NaOH but turns brown.

Mn2+ is confirmed

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(3) Dissolve the 1(a) in aqua regia, evaporate to Dryness, add 1ml of distilled water and divide the resultant product into two parts. Part (1) + 1 ml of amyl alcohol + 100 mg of solid NH4SCN and stir it.

A Blue colour in the alcohol layer is obtained.

Co2+ is confirmed

Part (2) + 5 drops of dimethyl glyaxime reagent + NH4OH.

A pink ppt. is obtained.

Ni2+ is confirmed.

FIFTH GROUP OF BASIC RADICALS The basic radicals of this group are Ca2+, Sr2+ & Ba2+ .The group reagent is NH4Cl(s) + NH4OH and (NH4)2 CO3.

EXPERIMENT

OBSERVATION

INFERENCE

(a) A white ppt. is obtained.

May be Ca2+, Sr2+ or Ba2+

Part (1) + Potassium chromate solution.

A yellow ppt. is obtained.

May be Ba2+ .

Part (2) + Calcium Sulphate Sol. and heat.

A thin white ppt. is obtained.

May be Sr2+ .

Part (3) + Ammonium exalate solution.

A white ppt. is obtained.

May be Ca2+ .

(a) Apple green coloured flame is obtained.

Ba2+ is confirmed.

(b) Crimson red coloured flame is obtained.

Sr2+ is confirmed.

(c) Brick red coloured flame is obtained,

Ca2+ is confirmed.

(1) Original solution + NH4Cl(s) + NH4OH in excess + (NH4)2 CO3 solution. (2) Dissolve the white ppt. obtained in small amounts of dilute acetic acid. Divide the solution in three parts.

(3)Flame tests: Make a paste of the given salt with few drops of Conc. HCl in a watch glass. Heat a Pt. wire in non luminous flame till no colour is imparted to the flame. Dip the Pt. wire in the paste and hold it in the flame.

SIXTH GROUP OF BASIC RADICALS EXPERIMENT (1) Original solution + excess of NH4OH + Ammonium Hydrogen Phosphate.

OBSERVATION A white ppt. is obtained.

INFERENCE Mg2+ is confirmed.

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