Experiment no. 6 Identification test for Cations & anions

• Magnesium hydroxide 
• Ferrous sulphate 
• Sodium  Bicarbonate 
• Copper sulphate

Aim: To perform the identification test for ferrous sulphate

Reference: Dr. N. Sharma, Practical Inorganic Pharmaceutical Chemistry And Viva Voce, Birla Publications Pvt. Ltd., I^st edition, Page no. 83-84.

Requirements:
Chemicals & Reagents: Ferrous sulphate crystals, dilute H₂SO₄, phenanthroline, ceric ammonium sulphate, potassiun ferricyanide, dilute HCl, potassiun ferrocyanide, barium chloride, lead acetate, ammonium acetate, dilute NaOH, iodine solution, strontium chloride.
Glassware: Test tube, beaker, funnel watch glass, spatula

Chemical Formula: FeSO₄.7H₂O

Theory: Ferrous sulfate occurs as a crystalline bluish green powder. It has a tendency to rapidly oxidize on exposure to moist air. It is odorless and is characterized through its metallic taste (styptic) taste. It is soluble in water but insoluble in alcohol.

Use: It is used as an important hematinic agent in various iron formulations for treatment of anemia.

The identification reactions for ferrous sulphate are summarized as below:

A)A) Identification test for Fe⁺²

Sr. No	Test	Observation	Inference
1.	To a small quantity of salt, add dilute H2SO4 and phenanthroline	Red colouration	Fe+2 may be present
2.	Add ceric ammonium sulphate	Red colour discharged	Fe+2 is confirmed
3.	Take salt and add potassiun ferricyanide	Blue precipitates observed	Fe+2 is confirmed
4.	Add dilute HCl	Precipitates are insolube	Fe+2 ion confirmed
5.	Take salt and add potassiun ferrocyanide and add dilute HCl	White precipitates are formed and rapidly becomes blue	Fe+2 may be present
6.	Add dilute HCl	The precipitates are insoluble	Fe+2 is confirmed

 Result: The given sample contains Fe⁺² cations.

B) Identification test for SO₄^2-

Sr. No	Test	Observation	Inference
1.	To a small quantity of salt, add water with dilute HCl and BaCl2	White precipitate	SO42- may be present
2.	Take salt and add lead acetate	White precipitate	SO42- may be present
3.	Add CH3COONH4 with NaOH	Precipitate dissolve	SO42- ion confirmed
4.	Take salt and add iodine solution	Suspension of yellow colour is obtained	SO42- may be present
5.	To the above suspension, add SnCl2 and boil the mixture	No colour precipitate obtained	SO42- ion confirmed

 Result: The given sample contains SO₄^2- anions. 

Aim: To perform the identification test for sodium bicarbonate

Reference: H.G Raval, Practicals in Inorganic and Analytical Chemistry, Nirav and Roopal Prakasan, I^st edition, Page no. 39.

Requirements:

Chemicals & Reagents: Sodium bicarbonate powder, pyroantimonate, Zinc uranyl acetate, dilute HCl, BaCl₂ solution, freshly prepared silver nitrate solution.

Glassware: Test tube, beaker, funnel watch glass, spatula

Chemical formula: NaHCO₃

Theory: Sodium bicarbonate is a white solid crystalline compound composed of sodium ions and bicarbonate ions. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). Sodium bicarbonate is also known as baking soda.

Use: Sodium bicarbonate is used to relieve heartburn, sour stomach, or acid indigestion by neutralizing excess stomach acid.

Category: Antacid

Reactions:

2 Na⁺ + K₂H₂Sb₂O₇     →                 Na₂H₂Sb₂O₇ (white precipitate) + 2K⁺

Na₂CO₃ + BaCl₂            →                  BaCO₃ (white precipitates) + 2NaCl

Na₂CO₃ + 2HCl             →                   2NaCl + H₂O + CO₂

Na₂CO₃ + 2AgNO₃      →                  Ag₂CO₃ (white precipitate) + 2NaNO₃

The identification reactions for sodium bicarbonate are summarized as below:

A) Identification test for Na⁺

Sr. No	Test	Observation	Inference
1.	Pyroantimonate is added to prepared original solution	White precipitates	Na+ is present
2.	Zinc Uranyl acetate is added to prepared original solution	Yellow precipitates	Na+ ion is confirmed

 Result: The given sample contains Na⁺ cations

 B) Identification test for CO₃^2- 

Sr. No	Test	Observation	Inference
1.	O.S. + dilute HCl	The effervescence of CO2 gas that turns lime water milky	CO32- is present
2.	O.S. + BaCl2 solution	White precipitates soluble in dilute acid along with effervescence and also soluble in excess of BaCl2	CO32- is present
3.	O.S. + AgNO3	White precipitates that turn yellow on adding an excess of the reagent and the precipitates dissolved rapidly in dilute HNO3 or ammonia	CO32- ion is confirmed

 Result: The given sample contains CO₃^2- anions.

Aim: To perform the identification test for copper sulphate

Reference: H.G Raval, Practicals in Inorganic and Analytical Chemistry, Nirav and Roopal Prakasan, I^st edition, Page no. 22.

Requirements:

Chemicals & Reagents: Copper sulphate powder, potassium ferrocyanide, H₂S water, dilute NaOH, dilute NH₄OH, potassium iodide solution, barium chloride solution, lead acetate, ammonium acetate, dilute NaOH, iodine solution, strontium chloride.

Glassware: Test tube, beaker, funnel watch glass, spatula

Chemical formula: CuSO₄.5H₂O

Theory:

Cupric sulfate is a white or off-white solid. The anhydrous salt is colourless but the hydrated salt is blue in colour. It readily dissolves in water but is insoluble in alcohol. The pentahydrate (CuSO₄·5H₂O), the most commonly encountered salt, is bright blue. 

Uses:  It is a potent emetic and is used as an antidote for poisoning by phosphorus.

Reactions:

2CUSO₄ + K₄Fe (CN) 6   →  Cu₂ [Fe (CN) ₆] (reddish brown ppt) + 2K₂SO₄

Cu⁺² + S^-2    →  CuS (black ppt)

Cu⁺² + 2OH^-    →    Cu(OH)₂ (blue ppt) and Cu(OH)₂               CuO (black ppt)

2 CuSO₄ + 2NH₄OH →  (NH₄)₂SO₄ + CuSO₄.Cu(OH)₂ (bluish green ppt)

Cu⁺² + 4I^-   →  Cu₂I₂ (white ppt) + I₂

SO₄^-2 + BaCl₂       →    BaSO₄ (white ppt) + 2NaCl

 The identification reactions for copper sulphate are summarized as below:

A) Identification test for Cu⁺²

Sr. No	Test	Observation	Inference
1.	O.S. + K4Fe(CN)6	Reddish brown ppt obtained	Cu+2 is present
2.	O.S. + H2S	Black precipitates	Cu+2 is present
3.	O.S. + NaOH	Blue precipitates	Cu+2 is present
5.	O.S. + NH4OH	Bluish green precipitate which dissolves in excess ammonia	Cu+2 ion is confirmed
6.	O.S. + KI	Greenish white or brown precipitates	Cu+2 ion is confirmed

 Result: The given sample contains Cu⁺² cations

 

B) Identification test for SO₄^2-

Sr. No	Test	Observation	Inference
1.	To a small quantity of salt, add water with dilute HCl and BaCl2	White precipitate	SO42- may be present
2.	Take salt and add lead acetate	White precipitate	SO42- may be present
3.	Add CH3COONH4 with NaOH	Precipitate dissolve	SO42- ion confirmed
4.	Take salt and add iodine solution	Suspension of yellow colour is obtained	SO42- may be present
5.	To the above suspension, add SnCl2 and boil the mixture	No colour precipitate obtained	SO42- ion confirmed

 Result: The given sample contains SO₄^2- anions

Aim: To perform the identification test for magnesium hydroxide

Reference: H.G Raval, Practicals in Inorganic and Analytical Chemistry, Nirav and Roopal Prakasan, I^st edition, Page no. 22.

Requirements:

Chemicals & Reagents: Magnesium hydroxide powder, Ammonia solution, ammonium chloride solution, sodium hydrogen phosphate, litmus paper, HgCl₂ solution

Glassware: Test tube, beaker, funnel watch glass, spatula

Chemical formula: Mg(OH) ₂

Theory: Magnesium hydroxide is a white solid with low solubility in water Magnesium is important for many systems in the body especially the muscles and nerves. Magnesium hydroxide is used as a laxative to relieve occasional constipation (irregularity) and as an antacid to relieve indigestion, sour stomach, and heartburn.

Uses: Magnesium hydroxide is a common component of antacids, such as milk of magnesia, as well as laxatives.

Reactions:

Mg²⁺ + Na₂HPO₄ + NH₃      →      Mg (NH₄) PO₄  (white part)

 A) Identification test for Mg²⁺

Sr. No	Test	Observation	Inference
1.	Take 15 mg of substance being examined. Add 2 ml of H2O and 1 ml of dilute NH3 solution.	A white precipitate is formed	Mg2+ may be present
2.	To the above solution, add 1 ml of 2 M NH4Cl	Precipitates redissolves	Mg2+ confirmed
3.	Add 1 ml of 0.25 M of Na2HPO4	A white crystalline ppt is formed

 Result: The given sample contains Mg²⁺ cations

 B) Identification test for OH^-

Sr. No	Test	Observation	Inference
1.	Perform litmus paper test for O.S	Red litmus paper turns to blue	OH- may be present
2.	O.S. + HgCl2 solution	Yellow precipitates	OH- is confirmed

 Result: The given sample contains OH^- anions

To identify cation & anion in given pharmaceutical compounds.

 REFERENCE:

1.        Singh H.R., Kapoor V.K. “Practical Pharmaceutical chemistry”, Vallabh Prakashan, Ed I^st, 2008, pp 19-25

2.        Chatwal GR, “Pharmaceutical chemistry inorganic” Himalaya publishing house, Ed 5^th, 2010, pp 437-439

 

OBSERVATION:

S.NO.	IONS	TEST	OBSERVATION	INFERENCE
1.	Acetate	a)    original solution + dil. H2SO4 b)    original solution + FeCl3	Smell of vinger     Radish brown ppt	Acetate may be present. Acetate confirmed.
2.	Chloride	a)    Salt +conc. H2SO4 take a rod dipped in NH3 solution to mouth of test tube. b)    salt + water + dil. HNO3 + AgNO3	Pungent smell ,white fumes of NH4Cl obtained     Curdy white ppt	Cl- may be present.         Cl- confirmed.
3.	Iodide	a) salt + water + dil. HNO3 +AgNO3	Yellow colour	I- present
		b) salt + conc H2SO4	Violet fumes obtain	I- present
4.	Bromide	a)    salt + conc.H2SO4       b)    original solution + Cl- solution + 2-3 drop of CHCl3	Reddish brown fumes obtained which intensity on adding MNO2 Reddish color.	Br- may be present.     Br- confirmed.
5	Carbonate	a)    salt + dil. H2SO4 if CO2 is passed to lime water, it turns milky b)    original solution + MgSO4	Effervescence obtained due to libration of CO2   White ppt obtained	CO3 - - may be present     CO3 - - confirmed.

6.	Sulphate	a)             substances      + BaCl2     b)      Original solution + lead acetate.	White ppt White ppt	SO4 - - may be present. SO4         -         - confirmed.
7.	Nitrate	a)      Original solution + conc. H2SO4 + FeSO4                 during heating add copper chips. b)      Original solution + FeSO4 gradually add conc. H2SO4	Reddish brown fumes         Brown ring is formed at the junction of 2 layer.	NO3 - - may be present.         NO3         -         - confirmed.
8.	Bicarbonate	a) Original solution + MgSO4	No ppt then boil white ppt formed	HCO3 - Present