cations reactions

33
Cations reactions 1 REACTIONS OF DETECTION OF CATIONS OF THE FIRST ANALYTICAL GROUP Reactions of lithium cations detection: 1. Action of carbonate ammonium . Carbonates of alkaline metals and ammonium form white precipitate: (NH 4 ) 2 CO 3 + 2LiCl Li 2 CO 3 + 2NH 4 Cl Lithium carbonate soluble in diluted mineral acids and in acetic acids and does not precipitate in presence of ammonium salts. 2. Action of sodium hydrogenphosphate . Na 2 HPO 4 in neutral or slightly acidic solution forms white precipitate: 3LiCl +2Na 2 HPO 4 Li 3 PO 4 + NaH 2 PO 4 + 3NaCl Lithium phosphate easily soluble in solutions of acids, insoluble in alcohol and soluble in ammonium salts. 3. Action of sodium hexanitrocobaltate (III). The sodium hexanitrocobaltate (ІІІ) in the neutral or acetic solution forms yellow crystalline precipitate similar to potassium salt: 3LiCl + Na 3 [Cо(NO 2 ) 6 ] Li 3 [Cо(NO 2 ) 6 ] + 3NaCl 4. Action of ammonium fluoride. In presence of NH 4 OH ammonium fluoride gives white amorphous precipitate: LiCl + NH 4 F Li F+ NH 4 Cl It is possible to use this reaction for the separation of lithium ions from ions of potassium and sodium. 5. Action of potassium orthoperiodate of iron(III) . K 2 [FeIO 6 ] in neutral or alkali environment at heating forms yellow amorphous sediment LiK[FeIO 6 ]: LiCl + K 2 [FeIO 6 ] LiK[FeIO 6 ] + KCl 6. Flame test. Salts of lithium paint colourless flame of gas burner in the intensively red colour. Reactions of potassium cations detection: 1. Action of sodium hidrogentartrate or tartaric acid. The sodium hydrogentartrate or tartaric acid at рН 4-5 form white crystalline precipitate: KCl + NaHC 4 H 4 O 6 KHC 4 H 4 O 6 + NaCl Precipitate potassium hydrogentartrate forms super-saturated solutions. The precipitate dissolves in the hot water, alkalis and acids: KHC 4 H 4 O 6 +HCl H 2 C 4 H 4 O 6 + КCl KHC 4 H 4 O 6 +NaОН KNaC 4 H 4 O 6 + H 2 O

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  • Cations reactions 1

    REACTIONS OF DETECTION OF CATIONS OF THE FIRST ANALYTICAL GROUP

    Reactions of lithium cations detection:

    1. Action of carbonate ammonium. Carbonates of alkaline metals and ammonium form white precipitate:

    (NH4)2CO3 + 2LiCl Li2CO3 + 2NH4Cl

    Lithium carbonate soluble in diluted mineral acids and in acetic acids and does not precipitate in presence of ammonium salts.

    2. Action of sodium hydrogenphosphate. Na2HPO4 in neutral or slightly acidic solution forms white precipitate:

    3LiCl +2Na2HPO4 Li3PO4 + NaH2PO4 + 3NaCl

    Lithium phosphate easily soluble in solutions of acids, insoluble in alcohol and soluble in ammonium salts.

    3. Action of sodium hexanitrocobaltate (III). The sodium hexanitrocobaltate () in the neutral or acetic solution forms yellow crystalline precipitate similar to potassium salt:

    3LiCl + Na3[C(NO2)6] Li3[C(NO2)6] + 3NaCl

    4. Action of ammonium fluoride. In presence of NH4OH ammonium fluoride gives white amorphous precipitate:

    LiCl + NH4F Li F + NH4Cl

    It is possible to use this reaction for the separation of lithium ions from ions of potassium and sodium.

    5. Action of potassium orthoperiodate of iron(III). K2[FeIO6] in neutral or alkali environment at heating forms yellow amorphous sediment LiK[FeIO6]:

    LiCl + K2[FeIO6] LiK[FeIO6] + KCl

    6. Flame test. Salts of lithium paint colourless flame of gas burner in the intensively red colour.

    Reactions of potassium cations detection:

    1. Action of sodium hidrogentartrate or tartaric acid. The sodium hydrogentartrate or tartaric acid at 4-5 form white crystalline precipitate:

    KCl + NaHC4H4O6 KHC4H4O6 + NaCl

    Precipitate potassium hydrogentartrate forms super-saturated solutions. The precipitate dissolves in the hot water, alkalis and acids:

    KHC4H4O6 +HCl H2C4H4O6 + Cl KHC4H4O6 +Na KNaC4H4O6 + H2O

  • Cations reactions 2

    Reaction implementation features: For acceleration of precipitate formation the reaction make at cooling and rubbing by the glass stick on walls of test tube. Make reaction with the tartaric acid in presence of sodium acetate.

    2. Action of sodium hexanitrocobaltate (III). The sodium hexahydrocobaltate() at 4-5 forms yellow precipitate:

    2KCl + Na3[C(NO2)6] K2Na[C(NO2)6] + 2NaCl

    Precipitate is insoluble in acetic acid, dissolves at heating in the strong acids and decomposes by alkalis with formation of the brown precipitate C()3:

    K2Na[C(NO2)6] + 6HCl 2Cl + NaCl + CCl3 + 6NO2 K2Na[C(NO2)6] + 3Na C()3 + 2NO2 + 4NaNO2

    3. Action of hydrogen hexachloroplatinate (IV). Hydrogen hexachloroplatinate in neutral or weak acidic solution forms yellow crystalline precipitate:

    KCl + H2[PtCl6] K2[PtCl6] + 2HCl

    4. Action of perchloric acid. The perchloric acid forms white crystalline precipitate:

    KCl + HCl4 KCl4 + HCl

    The potassium perchlorate is partly soluble in water and insoluble in the butyl alcohol.

    5. Action of picric acid. Picric acid (trinitrophenol) sediments yellow precipitate from concentrated solutions of potassium salts:

    OHNO2O2N

    NO2

    OKNO2O2N

    NO2

    ++ KCl + HCl

    6. Action of dipicrylamine. Dipicrylamine in interaction with potassium-ions substitutes hydrogen of imide-group on potassium ion and forms orange-red precipitate:

    NH

    NO2

    NO2

    O2N

    O2N

    O2N

    NO2 NK

    NO2

    NO2

    O2N

    O2N

    O2N

    NO2+ KCl + HCl

    7. Flame test. Volatile salts of potassium (KCl) paint flame of gas burner in the pale-violet colour.

  • Cations reactions 3

    Reactions of sodium cations detection:

    1. Action of zinc-uranile-aceate. Zn[(UO2)3(CH3COO)8] in neutral or weak acidic solution gives green-yellow crystalline precipitate, which has brilliant yellow fluorescence:

    NaCl + Zn[(UO2)3(CH3COO)8] + CH3COO + 92 NaZn[(UO2)3(CH3COO)9]9H2O + HCl

    This reaction can be executed by the drop method. In case of irradiation by the ultraviolet light the green luminescence exists.

    2. Action of potassium hexahydroxystybiate. K[Sb(OH)6] in neutral environment forms white crystalline precipitate:

    NaCl + K[Sb(OH)6] Na[Sb(OH)6] + KCl

    Na[Sb(OH)6] precipitate is soluble in the hot water and partly in alkalis:

    Na[Sb(OH)6] + 2Na Na3SbO4 + 42

    The acids decompose the K[Sb(OH)6] reagent and formed precipitate Na[Sb(OH)6], creating amorphous precipitate of metha-stybiate acid:

    Na[Sb(OH)6] + Cl [Sb(OH)6] + NaCl [Sb(OH)6] SbO3 + 32

    3. Action of methoxy-phenyl-acetic acid. Solution of 4-methoxy-phenyl-acetic acid with sodium cations forms white crystalline precipitate:

    CH3O CH2COOH CH3O CH2COONa+ NaCl + HCl

    4. Flame test. The sodium salts paint colourless flame of gas burner in yellow. A test is very sensible to sodium ions.

    Reactions of ammonium cations detection:

    1. Action of magnesium oxide and sodium hexanitrocobaltate(III). Undergo magnesium oxide on solutions containing ammonium-ions forms ammonium. Formed ammonium after intersction with chloride acid and sodium hexanitrocobaltate(III) forms yellow precipitate:

    2NH4Cl + Na3[C(NO2)6] (NH4)2Na[C(NO2)6] + 2NaCl

    2. Action of alkalis. Alkalis at heating with ammonium salts evolve an ammonia:

    NH4Cl + Na NH3 + NaCl + 2

    Free ammonia detection methods: smell; moistened universal indicator paper, placed to opening test tube, from which an ammonia is

    eluted, becomes green-blue or dark blue;

  • Cations reactions 4

    smoke formation at placing a glass stick moistened by chloride acid; moistened mercury indicator paper, placed to opening test tube, from which an ammonia is

    eluted, colour in black as a result of reaction:

    2NH3 + Hg2(NO3)2 Hg + NH2HgNO3 + NH4NO3

    2. Action of the Nesslers reagent. The Nesslers reagent (K2[HgI4]) in alkaline environment with ammonium salts forms orange-brown precipitate of the Millons base:

    Hg

    HgO

    INH4Cl + 2K2[HgI4] + 4KOH H2N KCl + 7KI + H2O+

    Precipitate dissolves in chloride acid and in solutions of alkalis.

  • Cations reactions 5

    REACTIONS OF DETECTION OF CATIONS OF THE SECOND ANALYTICAL GROUP

    Reactions of silver cations detection:

    1. Action of chloride acid. Chloride acid and water-soluble chlorides form white amorphous precipitate:

    AgNO3 + HCl = AgCl + HNO3

    Silver chloride insoluble in diluted nitrate acid, easily soluble in the ammonia solutions and in ammonium carbonate:

    AgCl + 2N4O = [Ag(N3)2]Cl + 2H2O

    Addition of acid or potassium iodide solution to the got ammoniac solution of AgCl or AgI precipitate falls out:

    [Ag(N3)2]Cl + 2HNO3 = AgCl + 2N4NO3 [Ag(N3)2]Cl + 2KI = AgI + 2N3 + KCl

    2. Action of iodides. Potassium iodide forms light-yellow precipitate:

    AgNO3 + KI = AgI + KNO3

    Precipitate is practically insoluble in ammonia (unlike AgCl) and diluted nitrate acid, well soluble in solution of potassium cyanide and sodium thiosulphate.

    3. Action of hydroxides of alkaline metals and ammonium. The alkalis at first form white precipitate

    AgNO3 + NaOH = AgOH + NaNO3

    This compound quickly decomposes with formation of the brown precipitate Ag2O:

    2AgOH = Ag2O + 2

    Precipitate is insoluble in the alkali surplus, well soluble in nitrate acid and ammonia solution. The ammonia in case of addition by drops to the neutral solution of silver salt forms the brown precipitate Ag2O, which easily dissolves in the ammonia surplus:

    AgNO3 + N4OH = Ag2O + 2 + N4NO3 Ag2O + 4N4O = 2[Ag(N3)2]OH + 3H2O

    4. Action of hydrogen sulphide. Hydrogen sulphide or ammonia sulphide forms black precipitate:

    2AgNO3 + (N4)2S = Ag2S + 2N4NO3

    Silver sulphide dissolves in concentrated nitrate acid:

    3Ag2S + 8NO3 = 6AgNO3 + 2NO +3S + 42

  • Cations reactions 6

    5. Action of chromates. Salts of chromic acid form orange-red precipitate:

    2AgNO3 + 2CrO4 = Ag2CrO4 + 2NO3

    6. Action of dithizone. Dithizone (diphenylthiocarbazone) with the silver cations forms the complex compound painted in yellow, which is extracted by chloroform and carbon tetrachloride:

    NC SH

    N N

    NH NC SAg

    N N

    NH+ AgNO3 + HNO3

    7. Action to formaldehyde. Formaldehyde easily reduces the silver ion to free metal:

    Ag2O + O = 2Ag + HO

    As a result of reaction in the test tube walls appears the brilliant plaque of free silver, through what this reaction got a name reaction of silver mirror.

    Reactions of lead cations detection:

    1. Action of chloride acid. Chloride acid and chlorides with lead cations form white precipitate:

    Pb(NO3)2 + 2HCl = PbCl2 + 2HNO3

    Precipitate is soluble in the hot water and the HCl surplus.

    2. Action of hydroxides of alkaline metals and ammonium. Alkalis in the equivalent quantities to the lead form white precipitate:

    Pb(NO3)2 + 2NaOH = Pb(OH)2 + 2NaNO3

    Precipitate is soluble in acids and alkali surplus (at = 13) forming plumbite Na2PbO2. Ammonium hydroxide forms white precipitate of base salt insoluble in surplus of reagent:

    Pb(NO3)2 + N4OH = Pb(OH)NO3 + N4NO3

    3. Action of iodides. Potassium iodide with the lead salts forms yellow precipitate:

    Pb(NO3)2 + 2 = PbI2 + 2HNO3

    Precipitate is soluble in surplus of reagent, in hot water, and in acetic acid. Precipitate solubility in hot water and acetic acid is used for the additional detection of lead cations, since at cooling of solution the precipitate falls out again as character gold scales.

    4. Action of hydrogen sulphide. The hydrogen sulphide forms black precipitate:

  • Cations reactions 7

    b(NO3)2 + 2S = bS + 2NO3

    Lead sulphide does not dissolve in acetic and mineral acids, unless the concentrated nitrate acid:

    3bS + 8NO3 = 3b(NO3)2 + 2NO +3S + 42

    5. Action of sulphates. The water-soluble sulphates with the lead cations form the white precipitate:

    b(NO3)2 + Na2SO4 = PbSO4 + 2NaNO3

    6. Action of chromates. To potassium chromate forms yellow precipitate:

    b(NO3)2 + 2CrO4 = PbCrO4 + 2NO3

    7. Action to sodium of rhodizonate.

    ONa

    ONa

    O

    OO

    O O

    O

    O

    OO

    OPb+ Pb(NO3)2 + 2NaNO3

    8. Action of dithizone.

    N

    NH

    NC S SPb

    N N

    NH

    N

    NC

    N

    NH

    N

    NC SH2 + Pb(NO3)2

    + 2HNO3

    Reactions of mercury(I) cations detection:

    1. Action of chloride acid. The chloride acid with mercury() forms white precipitate:

    g2(NO3)2 + 2HCl = g2Cl2 + 2HNO3

    The precipitate has luminescence by orange-red colour in the ultraviolet light. Ammonia with mercury() chloride forms free mercury, from which the precipitate turns black, and white precipitate of mercury aminochloride (dismutation of univalent mercury on g+2 and g0):

  • Cations reactions 8

    g2Cl2 + 2N4O = gN2Cl + g + N4Cl + H2O

    2. Action of hydroxides of alkaline metals and ammonium. Hydroxides of alkaline metals with mercury() salt form black precipitate:

    g2(NO3)2 + 2NOH = g2O + 2 + 2NNO3

    Solution of ammonium hydroxide with mercury() salt forms a mixture, which consists of black elemental mercury and white mercury aminonitrate:

    g2(NO3)2 + 2N4OH = g + N2gNO3 +N4NO3+ 2

    3. Action of iodides. Potassium iodide with solutions of mercury() salts forms green-grey precipitate

    g2(NO3)2 + 2KI = g22 + 2KNO3

    Which dissolves in surplus of potassium iodide with colourless complex formation and elemental mercury:

    g22 + 2KI = K2[gI4] + g

    4. Action of hydrogen sulphide. The hydrogen sulphide forms mixture of elemental mercury and sulphide of bivalent mercury as a result of dismutation of g2S to gS and g:

    g2(NO3)2 + 2S = gS +g + 2NO3

    Mercury() sulphide dissolves in aqua regia:

    3gS + 6l + 2NO3 = 3gl2 + 3S + 2NO + 2O

    5. Action of tin(II) chloride. The mercury() reduces to free metal under action of tin():

    g2(NO3)2 + SnCl2 = g2Cl2 + Sn(NO3)2 g2Cl2 + SnCl2 = 2g + SnCl4

    6. Reaction on copper plate. If to drop solution of mercury() salt on the copper coin, through 2-3 min coin will be covered by the grey layer of mercury amalgam, which after grinding by the wool piece becomes brilliant:

    g2(NO3)2 + Cu = 2g + Cu(NO3)2

  • Cations reactions 9

    REACTIONS OF DETECTION OF CATIONS OF THE THIRD ANALYTICAL GROUP

    Reactions of calcium cations detection:

    1. Action of sulphate acid and soluble in water of sulphates. The sulphate acid and water-soluble sulphates with calcium ions form white crystalline precipitate:

    CaCl2 + H2SO4 = CaSO4 + 2HCl

    Saturated solution of ammonium sulphate dissolves precipitate forming a water-soluble complex:

    CaSO4 + (NH4)2SO4 = (NH4)2[Ca(SO4)2]

    This reaction uses for separation calcium ions from strontium ions.

    2. Action of ammonium oxalate. To the ammonium oxalate with calcium salts forms white crystalline precipitate:

    CaCl2 + (NH4)2C2O4 = CaC2O4 + 2NH4Cl

    Precipitate is insoluble in acetic acid (unlike to oxalates of barium and strontium) and ammonia solution, soluble in solutions of strong acids with oxalic acid formation:

    CaC2O4 + 2HCl = CaCl2 + H2C2O4

    3. Action of glyoxal-bis-(2-hydroxyaniline) (Pharmacopoeia). Glyoxal-bis-(2-hydroxyaniline) with calcium ions in alkali environment forms red complex compound. The product is hardly soluble in water but well extracts with chloroform.

    OHN

    CH

    OHN

    CH

    ON

    CH

    ON

    CH

    Ca

    + Ca(OH)2

    H2O H2O

    4. Action of potassium hexacyanoferrate(II) (Pharmacopoeia). Potassium hexacyanoferrate(II) at pH > 7 and ammonium chloride presence interacts with calcium ions and forms white crystalline precipitate:

    CaCl2 + 2NH4Cl + K4[Fe(CN)6] = Ca(NH4)2[Fe(CN)6] + 4KCl

    5. Action of sodium rhodizonate. Sodium rhodizonate in acidic environment forms violet precipitate with calcium ions:

  • Cations reactions 10

    ONa

    ONa

    O

    OO

    O O

    O

    O

    OO

    OCa+ CaCl2 + 2NaCl

    6. Flame test. Volatile salts of calcium paint flame of gas burner in orange-red colour.

    Reactions of strontium cations:

    1. Action of sulphate acid and soluble in water of sulphates. The sulphate acid and water-soluble sulphates with strontium ions form white crystalline precipitate:

    SrCl2 + H2SO4 = SrSO4 + 2HCl

    The strontium sulphate is possible to convert to carbonate by boiling with saturated solution of sodium or potassium carbonate.

    1. Action of ammonium oxalate. Ammonium oxalate with strontium salts forms white crystalline precipitate:

    SrCl2 + (NH4)2C2O4 = SrC2O4 + 2NH4Cl

    Precipitate is soluble in the acetic acid and in solutions of strong acids with oxalic acid formation:

    SrC2O4 + 2CH3COOH = Sr(CH3COO)2 + H2C2O4 SrC2O4 + 2HCl = SrCl2 + H2C2O4

    2. Action of gipseous water. The gipseous water (saturated solution CaSO4 22) with strontium ions forms white crystalline precipitate:

    SrCl2 + SO4 = SrSO4 + Cl2

    The precipitate appears after heating or at the room temperature after protracted standing.

    3. Action of chromates. To potassium chromate with strontium ions forms yellow precipitate:

    SrCl2 + K2CrO4 = SrCrO4 + 2KCl

    The strontium chromate is soluble in mineral and acetic acids.

    1. Action to sodium rhodizonate. Sodium rhodizonate in neutral environment forms brown precipitate with strontium ions:

  • Cations reactions 11

    ONa

    ONa

    O

    OO

    O O

    O

    O

    OO

    OSr+ SrCl2 + 2NaCl

    The red-brown spot forms on filter paper also. This spot disappears after chloride acid addition (precipitate dissolving).

    4. Flame test. Volatile salts of strontium paint flame of gas burner in the carmine-red colour.

    Reactions of barium cations:

    1. Action of sulphate acid and soluble in water sulphates. The sulphate acid and sulphates with barium ions form white crystalline precipitate:

    BaCl2 + H2SO4 = BaSO4 + 2HCl

    Precipitate is insoluble in diluted mineral acids.

    2. Action of potassium dichromate. Potassium dichromate in presence of sodium acetate with barium ions forms yellow crystalline precipitate:

    2BaCl2 + K2Cr2O7 + 2 + 23Na = 2BaCrO4 + 2KCl + 23 + 2NaCl

    Precipitate is soluble in mineral acids and insoluble in acetic acid.

    3. Action of sulphate acid and potassium permanganate. Sulphate acid in saturated solution of potassium permanganate with barium ions forms violet precipitate, which is not discoloured by reducers. The KMnO4 crystals are isomorphic to BaSO4 crystals and wedge to the barium sulphate crystalline grate:

    BaCl2 + H2SO4 + KMnO4= BaSO4+ KMnO4+ 2HCl

    4. Action of sodium rhodizonate. Sodium rhodizonate with barium salts forms red sediment. On filter paper arises red-brown spot that changes colour in red after chloride acid addition. It is specific reaction on barium ions:

    ONa

    ONa

    O

    OO

    O O

    O

    O

    OO

    OBa+ BaCl2 + 2NaCl

    5. Action of ammonium oxalate. Ammonium oxalate with barium ions gives white crystalline precipitate:

  • Cations reactions 12

    BaCl2 + (NH4)2C2O4 = BaC2O4 + 2NH4Cl

    Precipitate is soluble in boiling acetic acid and in solutions of mineral acids with oxalic acid formation.

    6. Flame test. Volatile barium salts paint flame of gas burner in the yellow-green colour.

  • Cations reactions 13

    REACTIONS OF THE FOURTH ANALYTICAL GROUP CATIONS DETECTION

    Reactions of aluminium cations detection:

    1. Action to sodium or potassium hydroxide. Hydroxides of alkaline metals with aluminium ions form white precipitate, soluble in reagent surplus:

    Al2(SO4)3 + 6NaOH = 2Al(OH)3 + 3Na2SO4 Al(OH)3 +3NaOH = Na3[Al(OH)6]

    Na3[Al(OH)6] = NaAlO2 + 2H2O +2NaOH

    2. Action of ammonium hydroxide. The ammonia solution in the neutral environment with aluminium ions forms white amorphous precipitate, insoluble in reagent surplus:

    Al2(SO4)3 + 6N4OH = 2Al(OH)3 + 3(N4)2SO4

    3. Hydrolysis of aluminium salts. In presence NH4Cl at heating aluminate hydrolyses with formation of Al(OH)3 precipitate :

    NaAlO2 + H2O +NH4Cl = Al(OH)3 + N3 + NaCl

    4. Action of cobalt nitrate (Tenards blue formation). Cobalt nitrate at ignition with aluminium salts on filter paper forms cobalt aluminate of dark blue colour, which named Tenards blue (colour of ash):

    2Al2(SO4)3 + 2Co(NO3)2 = 2Co(AlO2)2 + 4N2 + O2 + 6SO3

    5. Action of 8-oxyquinoline (oxyne). 8-oxyquinoline with aluminium ions at 4,5-10 forms the yellow inner-complex compound:

    OHN

    NO

    NO

    N

    O+ Al(OH)33 + 3H2OAl

    6. Action of alizarin. Alizarin red S with aluminium ions alkaline environment, created by NH4OH, forms bright red precipitate:

    Al2(SO4)3 + 6N4OH = 2Al(OH)3 + 3(N4)2SO4

  • Cations reactions 14

    O

    O

    OO Al

    OH

    + H2O

    O

    O

    OHOH

    + Al(OH)3

    Reactions of zinc cations detection:

    1. Action of sodium or potassium hydroxide. Hydroxides of alkaline metals with zinc ions forms white precipitate soluble in reagent surplus with zincates formation:

    ZnCl2 + 2NaOH = Zn (OH)2 + 2NaCl Zn (OH)2 + 2NaOH = Na2ZnO2 + 2H2O

    2. Action of ammonium hydroxide. Solution of ammonium hydroxide with zinc ions forms white precipitate, which dissolves in the reagent surplus with formation of tetra-ammine complex:

    ZnCl2 + 2NH3 +2H2O = Zn(OH)2 + 2NH4Cl Zn(OH)2 + 4NH3 = Zn[(NH3)4](OH)2

    3. Action of sodium sulphide. Sodium sulphide with zinc ions forms white precipitate insoluble in the acetic acid and soluble in diluted HCl:

    ZnCl2 + Na2S = ZnS + 2NaCl ZnS

    + 2HCl = ZnCl2 + H2S

    4. Action of cobalt nitrate (Rinmanns green formation). Cobalt nitrate at ignition with zinc salts on filter paper forms cobalt zincate of green colour, which named Rinmanns green (colour of ash):

    Zn(NO3)2 + Co(NO3)2 = CoZnO2 + 4N2 + O2

    5. Action of ammonium tetrarhodanomercurate. Ammonium tetrarhodanomercurate with zinc salts in weak acidic environment forms white crystalline precipitate:

    ZnCl2 + (NH4)2[Hg(SCN)4]= Zn[Hg(SCN)4] + 2 NH4Cl

    6. Action of potassium hexacyanoferrate(II). Potassium hexacyanoferrate(II) with zinc salts forms white precipitate:

    3ZnCl2 + 2K4[Fe(CN)6] = K2Zn3[Fe(CN)6]2 + 6KCl

    7. Action of dithizone. Dithizone with zinc ions forms red inner-complex soluble in the organic solvents:

  • Cations reactions 15

    N

    NH

    N

    NC S S

    N

    NH

    N

    NC SH

    N

    NH

    N

    NC + H2SO4

    2 + ZnSO4

    Zn

    Reactions of chrome(III) cations detection:

    1. Action of sodium or potassium hydroxide. Hydroxides of alkaline metals with chrome(III) ions form precipitate of

    green colour, soluble in reagent surplus due to it amphoterric properties:

    Cr2(SO4)3 + 6NaOH = 2Cr(OH)3 + 3Na2SO4

    2. Action of ammonium hydroxide. Solutions of ammonium hydroxide forms precipitate Cr(OH)3, partly soluble in the reagent surplus with formation of hexamine-chrome() hydroxide:

    Cr(OH)3 + 6NH4OH = [Cr (NH3)6](OH)3 + 6H2O

    3. Action of sodium hydroxide and hydrogen peroxide. Under H2O2 action in alkaline environment the chrome() passes to chrome(V) and forms chromates having yellow colour:

    2NaCrO2 + 3H2O2 +2NaOH = 2Na2CrO4 + 4H2O

    4. Action of oxidants. Under action of oxidants (KMnO4, Cl2, (NH4)2S2O8) in acidic environment are formed dichromates appears orange colour:

    Cr2(SO4)3 + 3(NH4)2S2O8 +42O = 2Cr2O7 + 3(NH4)2SO4 + 32SO4

    5. Reaction of perchromate acid formation. Under action of H2O2 on the formed dichromate-ion forms chrome peroxide Cr2O5 (or perchromic acid 2CrO6 ):

    Cr2(SO4)3 + 8NaOH = 2NaCrO2 + 3Na2SO4 + 4H2O 2NaCrO2 + 3H2O2 +2NaOH = 2Na2CrO4 + 4H2O 2Na2CrO4 + H2SO4 = Na2Cr2O7 + Na2SO4 + H2O

    2SO4 + Na2Cr2O7 + 4H2O2 = 2H2CrO6 + Na2SO4 + 3H2O.

    If to reactionary mixture add a mixture of isoamyl alcohol with diethyl ether and shake up, an overhead layer is painted in the dark blue colour as a result of transition in alcohol-ether layer of chrome peroxide (perchromic acid).

  • Cations reactions 16

    Reactions of tin(II) cations detection:

    1. Action of sodium or potassium hydroxide. Hydroxides of alkaline metals with tin() salts forms white precipitate, soluble in surplus of alkali and acids

    :

    SnCl2 + 2NaOH = Sn(OH)2 + 2NaCl Sn(OH)2 + 2Na = Na2SnO2 + 22

    Sn(OH)2 + 2Cl = SnCl2 + 2H2O

    In case in presence of hydrogen peroxide the sodium stannite across to sodium stannate:

    Na2SnO2 + 22 = Na2SnO3 + 2

    2. Action of ammonium hydroxide. Ammonium hydroxide with Sn+2 ions forms white precipitate, insoluble in surplus of reagent:

    SnCl2 + 2N4OH = Sn(OH)2 + 2N4Cl

    3. Action of hydrogen sulphide, solubility of sulphides. Hydrogen sulphide or ammonium sulphide with solutions of tin() salts form dark-brown precipitate:

    SnCl2 + H2S = SnS + 2HCl

    SnS precipitate is insoluble in alkalis and in surplus of sodium sulphide, but easily dissolves in ammonium polysulphide with thio-salts formation:

    SnS + (NH4)2S2 = SnS2 +(NH4)2S SnS2 +(NH4)2S2 = (NH4)2SnS3 +S

    4. Action of salts of bismuth(III) and mercury() in alkaline environment. Tin(II) easily enter to oxidation-reducing reaction as reducer. Typical is oxidising-reducing reaction with salts of bismuth(III) and mercury(II) in the alkaline environment. As a result of reactions the precipitations of element mercury and bismuth sediment:

    Snl2 + 4Na = Na2SnO2 + 22+ 2NaCl Na2SnO2 + 2gCl2+ 2NaOH = Na2SnO3 + 2g + 4NaCl +H2O

    3Na2SnO2 + 2Bi(NO3)3+ 6NaOH = 3Na2SnO3 + 2Bi + 6NaNO3 +3H2O

    Reactions of tin(IV) cations detection:

    1. Action of sodium or potassium, or ammonium hydroxides. Hydroxides form white precipitate, which has amphoteric properties:

    H2[SnCl6]+ 6Na = H2[Sn(OH)6] + 6NaCl

    Precipitate is soluble in the alkali surplus:

    H2[Sn(OH)6] + 2Na = Na2[Sn(OH)6] + 22O.

    In acids the precipitate dissolves with formation of complex salts:

  • Cations reactions 17

    H2[Sn(OH)6] + 6Cl = H2[SnCl6] + 62O.

    2. Action of hydrogen sulphide. With the hydrogen sulphide the tin(IV) salt forms yellow precipitate:

    H2[SnCl6] + 2H2S = SnS2 + 6HCl.

    Precipitate is soluble in concentrated chloride acid:

    SnS2 + 6HCl = H2[SnCl6] +2H2S.

    Unlike Sn+2 salts the sulphide of Sn+4 is soluble in (NH4)2S solution:

    SnS2 + (NH4)2S = (NH4)2SnS3.

    3. Test with metallic iron. Unlike Sn+2 Sn+4 does not proceed in ions of bismuth and mercury, however in acidic environment is reduced by iron to Sn+2:

    H2[SnCl6] + Fe = FeCl2 + SnCl2 + 2HCl

    4. Action of cupferron. Cupferron (ammonium salt of N-nitrozo-phenyl-hydroxyl-amine) with tin(IV) ions forms yellow hardly soluble compound:

    NO Sn

    NO NO NO

    NOON

    NO

    ON

    NONH4

    NO+ 2NH4OH+ H2[SnCl6] 4

    + 6 NH4Cl + 2H2O

    Reactions of arsenic(III) cations detection:

    1. Action of sodium hypophosphite. Sodium hypophosphite in acidic environment reduces compounds of arsenic(III) and arsenic(V) to free arsenic, which forms sediment of brown colour or paints solution in the brown colour:

    NaH2PO2 + HCl = NaCl + H3PO2 As2O3 + 3H3PO2 = 2As + H3PO3

    2. Action of sodium hydroxide and hydrogen peroxide. In alkaline environment under action of hydrogen peroxide As+3 transforms to As+5:

    Na3AsO3 + H2O2 = Na3AsO4 + H2O

  • Cations reactions 18

    3. Action of sulphides. The sulphides in strong acidic environment with arsenic salts form yellow precipitate:

    2Na3AsO3 + 3H2S + 6HCl = As2S3 + 6NaCl + 3H2O

    Arsenic sulphide is soluble in solutions of sodium hydroxide, sodium sulphide, ammonium polysulphide, and ammonium carbonate and insoluble in concentrated chloride acid:

    As2S3 + 6NaOH = Na3AsS3 + Na3AsO3 + 3H2O As2S3 + 3Na2S = 2Na3AsS3

    As2S3 + 3(NH4)2S2 = 2(NH4)3AsS4 +S As2S3 + 3(NH4)2CO3 = (NH4)3AsS3 + (NH4)3AsO3 + 3CO2

    4. Action of silver nitrate. In neutral or alkaline environment silver nitrate with anion AsO33 forms yellow precipitate:

    Na3AsO3 + 3AgNO3 = 3Ag3AsO3 + 3Na NO3

    Precipitate is soluble in solutions of nitric and acetic acids, and also in solution of ammonium hydroxide.

    5. Action of iodine solution. In weak alkali environment under act of free iodine AsO33 ions transforms in AsO34, discolouring thus iodine solution:

    Na3AsO3 + I2 + 2NaHCO3 = Na3AsO4 + 2NaI + 2CO2 + H2O

    6. The Marshs test. The very small quantities of arsenic (< 0,1 mg) are well detected as arsine AsH3, which get after reducing of arsenic:

    2Na3AsO3 + 6Zn + 9H2SO4 = 2AsH3 +6ZnSO4 + 3Na2SO4 +6H2O

    Formed colourless arsine

    decomposes at heating with formation of free arsenic:

    2AsH3 = 2As + 3H2

    7. The Gutzeits test. Formed after presented highly reactions arsine forms with silver nitrate yellow complex, which decomposes under action of moisture to metallic silver:

    AsH3 + AgNO3 = [AsAg6(NO3)3] + 3HNO3 [AsAg6(NO3)3] + 3H2O = H3AsO3 + 6Ag + 3HNO3

    For the AsH3 detection use a paper, saturated by alcoholic solution of HgCl2. In this case vapour of arsine form orange or yellow colouring:

    AsH3 + 3HgCl 2 = As(HgCl)3 + 3HCl

    It is possible also to detect the AsH3 presence in case of his admission through pipe with the crystalline iodine. Thus forms arsenic iodide having red colour:

    AsH3 + 32 = As3 + 3H

  • Cations reactions 19

    Reactions of arsenic(V) cations detection:

    1. Action of sodium hypophosphite. Sodium hypophosphite in acidic environment reduces arsenic(III) and arsenic(V) to free arsenic, which forms sediment of brown colour or paints solution in the brown colour:

    NaH2PO2 + HCl = NaCl + H3PO2 As2O5 + 5H3PO2 = 2As + 5H3PO3

    2. Action of sulphides. Sulphides in strong acidic environment with arsenic salts form yellow precipitate:

    2Na3AsO4 + 5H2S + 6HCl = As2S5 + 6NaCl + 3H2O

    The arsenic sulphide is soluble in solutions of sodium of hydroxide, sodium sulphide, ammonium polysulphide, and ammonium carbonate:

    As2S5 + 6NaOH = Na3AsS4 + Na3AsO3S + 3H2O As2S5 + 3Na2S = 2Na3AsS3 + 2S

    As2S5 + 3(NH4)2S2 = 2(NH4)3AsS4 +3S As2S5 + 3(NH4)2CO3 = (NH4)3AsS4 + (NH4)3AsO3S + 3CO2

    3. Action of silver nitrate. In the neutral or alkaline environment silver nitrate with anion AsO43 forms precipitate of chocolate colour:

    Na3AsO4 + 3AgNO3 = 3Ag3AsO4 + 3Na NO3

    Precipitate is soluble in solutions of nitric and acetic acids, and in solution of ammonium hydroxide.

    4. Action of potassium iodide. Potassium iodide in acidic environment reduces AsO43 to AsO33, the brown colouring of free iodine thus appears:

    Na3AsO4 + 2I + 2HCl = Na3AsO3 + I2 + 2KCl + H2O

    5. Action of magnesial mixture. Magnesial mixture with arsenate-ions forms white crystalline precipitate, soluble in chloride acid:

    Na2HAsO4 + MgCl2 + NH4OH = MgNH4AsO4 + 2NaCl + H2O

    6. Action of molybdenum liquid. In acidic environment ammonium molybdate with arsenate-ions forms yellow precipitate:

    12(NH4)2 MoO4 + (NH4)3AsO4 + 24HNO3 = (NH4)3AsO412MoO3 + 24NH4NO3 + 10H2O

    7. The Marshs test. The very small quantities of arsenic (< 0,1 mg) are well detected as arsine AsH3, which get after reducing of arsenic:

    2Na3AsO4 + 8Zn + 11H2SO4 = 2AsH3 +8ZnSO4 + 3Na2SO4 +8H2O

    Formed colourless arsine

    decomposes at heating with formation of free arsenic:

    2AsH3 = 2As + 3H2

    Reactions of arsine detection are presented among reactions of arsenic (III).

  • Cations reactions 20

    Reactions of Detection of the Fifth Analytical Group Cations

    Reactions of magnesium cations detection:

    1. Action of ammonium and sodium hydroxide. Ammonium and sodium hydroxide with cations to magnesium form white amorphous precipitate, soluble in acids and salts of ammonium:

    MgCl2 + 2NaOH = Mg(OH)2 + 2NaCl

    2. Action of sodium monohydrogenphosphate. Sodium hydrogenphosphate in presence of the chloride ammonium and ammonium hydroxide with magnesium salts forms white crystalline precipitate:

    MgCl2 + Na2HPO4 + NH4OH = MgNH4PO4 + 2NaCl + H2O

    Precipitate is soluble in the strong acids and acetic acid:

    MgNH4PO4 + 3HCl = H3PO4 + MgCl2 + NH4Cl MgNH4PO4 + 2CH3COOH = Mg(CH3COO)2 + NH4H2PO4

    3. Action of 8-oxyquinolone (luminescence test). 8-oxyquinoline with magnesium ions to at 9-12 forms oxyquinolate fluorescing by the green colour:

    NOH N

    O

    N

    O+ Mg(OH)2 2 + 2H2OMg

    The reaction is performed on filtration paper.

    4. Action of magnesone- and magnesone-. Magnezone- (p-nitrobenzenazoresorzinole) and magnesone- (p-nitrobenzenazonaphthole) in the alkaline environment adsorb on Mg(OH)2 precipitate, changing thus red-violet colour on dark blue:

    5.

    N NO2N OH

    OH

    N NO2N OH

    OH OMg

    + H2O

    + HO-Mg-OH

    Magnesone-

  • Cations reactions 21

    N NO2N

    OH

    N NO2N

    OH OMg

    + H2O

    + HO-Mg-OH

    Magnesone-

    Reactions of iron(II) cations detection:

    1. Action of ammonium hydroxide and sodium hydroxide. Ammonium hydroxide and sodium hydroxide with the iron() ions form amorphous grey-green precipitate, soluble in acids:

    FeSO4 + 2NaOH = Fe(OH)2 + Na2SO4

    The precipitate quickly oxidises on air, changing colour to red-brown.

    2. Action of ammonium sulphide. Ammonium sulphide with the iron() salts forms black precipitate, soluble in diluted mineral acids:

    FeSO4 + (NH4)2S = FeS + (NH4)2SO4

    3. Action of potassium hexacyanoferrate(III). Potassium hexacyanoferrate() with the iron() salts forms dark blue precipitate:

    3FeSO4 + 2K3[Fe(CN)6] = Fe3[Fe(CN)6]2 + 3K2SO4

    The precipitate does not dissolve in acids, but decomposes by alkalis. The reaction is specific.

    4. Action of dimethylglioxime. Diacethyldioxime in the ammonium environment with the iron() ions forms soluble complex halving red colour :

    CH3

    CH3 NOH

    N-O

    CH3

    CH3N

    OH

    O-N C

    CCH3

    CH3 N-OH

    N-OHC

    C

    C

    CFe + H2SO42 + FeSO4

    5. Action of dipyridile. 2,2-dipyridile or o-phenanthroline in acidic environment with the iron() ions forms inner-complex compound halving crimson colour:

  • Cations reactions 22

    N

    N

    N

    N

    N

    NFe SO4

    + FeSO42

    6. Action of oxidants (KMnO4, 2). Oxidants in acidic environment oxidise the iron() ion to iron() ion:

    10FeSO4 + 2KMnO4 + 8H2SO4 = 5Fe2(SO4)3 + 2MnSO4 + K2SO4 + 8H2O 2FeSO4 + I2 + H2SO4 = Fe2(SO4)3 + 2HI

    Colour of oxidisers crimson of potassium permanganate or yellow of iodine disappear.

    Reactions of iron(III) cations detection:

    1. Action of ammonium hydroxide and sodium hydroxide. Ammonium hydroxide and sodium hydroxide with the iron() ions form amorphous red-brown precipitate, soluble in acids and insoluble in alkali surplus:

    FeCl3 + 3NaOH = Fe(OH)3 + 3NaCl

    3. Action of sodium sulphide. Sodium sulphide with solutions of iron() salts forms black precipitate, soluble in mineral acids:

    2FeCl3 + 3Na2S = Fe2S3 + 3NaCl

    4. Action of potassium hexacyanoferrate(). Potassium hexacyanoferrate() in slightly acidic environment with the iron() salts forms navy precipitate of Berlin blue:

    4FeCl3 + 3K4[Fe(CN)6] = Fe4[Fe(CN)6]3 + 12KCl

    The precipitate does not dissolve in the mineral acids, but soluble in solution of oxalic acid with the complex formation. The reaction is specific.

    5. Action of thiocyanates. Potassium or ammonium thiocyanate in slightly acidic environment with the iron() salts form the complex halving bloody-red colour:

    FeCl3 + 3KSCN = Fe(SCN)3 + 3KCl

    6. Action of sodium acetate. Sodium acetate with the iron() ions at cold forms iron() acetate with red-brown colour:

    FeCl3 + 3CH3COONa = Fe(CH3COO)3 + 3NaCl

  • Cations reactions 23

    If to dilute solution by water and to boil, the formed compound hydrolyses with formation of basic salt, which falls as brown precipitate:

    Fe(CH3COO)3 + 2H2O = Fe(OH)2(CH3COO) +2CH3COOH

    7. Action of potassium iodide. Potassium iodide reduces the iron() ions to the iron(II) ions. As a result of reaction an iodine forms and solution changes colour to brown:

    2FeCl3 + 2KI = 2FeCl2 + I2 + 2KCl

    If to the test-tube add few drops of benzene or chloroform and shake mixture, the iodine will pass to organic solvent and change colour of organic phase on violet.

    8. Action of sulphosalicylic acid. Sulphosalicylic acid in acidic solutions ( 1,8 2,5) with the iron() ions forms stabile complex with red-violet colour:

    SO3H

    COOHOH

    SO3

    COOOH

    Fe OH + HCl+ FeCl3

    At the indicated acidity the reaction is specific for iron() ions.

    Reactions of manganese(II) cations detection:

    1. Action of sodium hydroxide and ammonium hydroxide. Hydroxides of alkaline metals and ammonium hydroxide precipitate from solutions of manganese() salts the white precipitate Mn(OH)2, which changes to brown on air as a result of oxidisation by air oxygen to Mn(OH)2:

    MnSO4 + 2NaOH = Mn(OH)2 + Na2SO4 2Mn(OH)2 + H2O +O2 = 2Mn(OH)4

    Mn(OH)4 = MnO(OH)2 + H2O

    Precipitate is insoluble in alkalis, soluble in acids.

    2. Action of ammonium sulphide. Ammonium sulphide with manganese() cations forms light-brown precipitate:

    MnSO4 + (NH4)2S = MnS + (NH4)2SO4

    Precipitate is soluble in diluted mineral acids.

    3. Action of oxidants. Oxidants in acidic environment oxidise the manganese() cation to MnO4 anion, which in solutions has the character raspberry (crimcon) colour:

    ammonium persulphate:

    2MnSO4 + 5(NH4)2S2O8 + 8H2O = 2HMnO4 + 5(NH4)2SO4 + 7H2SO4

  • Cations reactions 24

    A reaction is performed at heating in presence AgNO3 catalyst.

    lead dioxide:

    2MnSO4 + 5PbO2 + 6HNO3 = 2HMnO4 + 2PbSO4 + 3 Pb(NO3)2 + 2H2O

    sodium bismuthate:

    2Mn(NO3)2 + 5NaBiO3+ 16HNO3 = 2HMnO4 + 5Bi(NO3)3 + 5NaNO3 + 7H2O

    Reactions of bismuth cations detection:

    1. Action of sodium hydroxide and ammonium hydroxide. The alkalis form white precipitate of bismuth hydroxide, which dissolves in acids and does not dissolve in alkalis:

    BiCl3 + 3NaOH = Bi(OH)3 + 3NaCl

    The bismuth hydroxide at boiling transfers to yellow bismuthyl hydroxide Bi(OH).

    2. Action of sodium sulphide. Sodium sulphide in acidic environment with the bismuth() salts gives brown-black precipitate:

    BiCl3 + 3Na2S= Bi2S3 + 6NaCl

    Precipitate is insoluble in the diluted acids, except concentrated nitrate acid:

    Bi2S3 + 8NO3 = 2Bi(NO3)3 + 2NO + 3S + 42

    3. Action of thiourea and sodium fluoride. Bismuth ions with thiourea forms various complexes with yellow colour:

    SNH2

    NH2

    SNH2

    NH2

    C

    9

    Bi(NO3)3 + 9 C Bi (NO3)3

    4. Action of potassium iodide. Potassium iodide precipitates from solutions of bismuth salts black precipitate BiI3, soluble in surplus of reagent with formation of yellow complex:

    BiCl3 + 3KI = BiI3 + 3KCl BiI3 + KI = [BiI4]

    5. Action of sodium stannite. Reducers (SnCl2) reduce ions of bismuth() to metallic bismuth, which falls as black precipitate:

    SnCl2 + 4NaOH = Na2SnO2 + 2NaCl + 2H2O Bi(NO3)3 + 3NaOH = Bi(OH)3 + 3NaNO3

    2Bi(OH)3 + 3Na2SnO2 = 3Na2SnO3 + 2Bi + 3H2O

  • Cations reactions 25

    6. Hydrolysis of bismuth salts. In case of dilution of bismuth salts solutions occurs hydrolysis with formation of compounds of bismuth() oxide (bismuthyl) BiO+ having white colour :

    BiCl3 + 2H2O = Bi(OH)2Cl + 2HCl Bi(OH)2Cl = BiOCl + H2O

    Precipitate is soluble in mineral acids and insoluble in tartaric acid.

    Reactions of antimony(III) [stibium(III)] cations detection:

    1. Action to sodium hydroxide and ammonium hydroxide. Alkalis and ammonium hydroxide with salts of antimony() form white precipitate:

    SbCl3 + 3NaOH = Sb(OH)3 + 3NaCl

    Fresh precipitate is soluble in alkalis with formation Na[Sb(OH)4] complex, and also in strong acids with formation of the proper salts.

    2. Action of hydrogen sulphide. Hydrogen sulphide with salts of antimony() in acidic environment forms orange-red precipitate:

    2SbCl3 + 3Na2S = Sb2S3 + 6NaCl

    Precipitate is soluble at heating in Na2S surplus with formation of thiosalts and also in solutions of alkalis:

    Sb2S3 + 3Na2S = 2Na3SbS3 Sb2S3 + 4NaOH = Na[Sb(OH)4] + Na3SbS3

    3. Action of metals. Cations of antimony in acidic environment reduces by metals, which are more active electrochemically zinc, tin, iron, aluminium; the metallic plate thus turns black:

    2SbCl3 + 3Zn = 2Sb + 3ZnCl2

    4. Hydrolysis of antimony (III) salts. Salts of antimony() in slightly acidic solutions hydrolyse forming salts of antimony() oxide (antimonyl) SbO white colour:

    SbCl3 + 2O = SbOCl + 2Cl

    5. Reaction with rhodamine B. Rhodamine B and other basic triphenylmethane dyes (methyl violet, diamond green) in chloride acid solution with chloride complex of antimony(V) form ionic associate insoluble in water and painted in violet colour:

    O

    COOH

    (C2H5)2N N (C2H5)2Cl+ _

    + H[SbCl6]

  • Cations reactions 26

    O

    COOH

    (C2H5)2N N (C2H5)2

    +

    [SbCl6] + HCl._

    The complex extracts by benzene and iso-propanole. For transformation of antimony() in antimony(V) add concentrated chloride acid and sodium nitrite.

    Reactions of antimony(V) cations detection:

    1. Action of sodium hydroxide and ammonium hydroxide. Alkalis and ammonium hydroxide with salts of antimony(V) form white precipitate:

    H[SbCl6] + 6NaOH = SbO(OH)3 + 6NaCl + 2H2O

    Precipitate is soluble in strong acids:

    SbO(OH)3 + 6HCl = H[SbCl6] +4H2O

    2. Action of hydrogen sulphide. Hydrogen sulphide with salts of antimony(V) in acidic environment forms orange-red precipitate:

    2H[SbCl6] + 52S = Sb2S5 + 12Cl

    Precipitate is soluble at heating in Na2S surplus with formation of thiosalts, and in solutions of alkalis:

    Sb2S5 + 3Na2S = 2Na3SbS4 4Sb2S5 + 18NaOH = 3Na[Sb(OH)6] + 5Na3SbS4

    3. Action of metals. Cations of antimony in acidic environment reduce by electrochemically more active metals (zinc, tin, iron, aluminium) to free antimony; the metallic plate thus turns black:

    2H[SbCl6] + 5Zn = 2Sb + 5ZnCl2 + 2HCl

    4. Hydrolysis of antimony(V) salts. At hydrolysis of salts of antimony(V) forms white precipitate of basic salt of antimony(V), soluble in surplus of chloride acid:

    H[SbCl6] + 2H2O = SbO2Cl + 5HCl

    5. Reaction with rhodamine B. Rhodamine B and other basic triphenylmethane dyes (methyl violet, diamond green) in chloride acid solution with chloride complex of antimony(V) form insoluble in water, painted in the violet colour ionic associate:

  • Cations reactions 27

    O

    COOH

    (C2H5)2N N (C2H5)2Cl+ _

    + H[SbCl6]

    O

    COOH

    (C2H5)2N N (C2H5)2

    +

    [SbCl6] + HCl._

    The complex well extracts by benzene and iso-propanole.

  • Cations reactions 28

    Reactions of the Sixth Analytical Group Cations Detection

    Reactions of cadmium cations detection:

    1. Action of ammonium hydroxide and sodium hydroxide. Ammonium hydroxide in equivalent quantities and sodium hydroxide with solutions of cadmium salts form white precipitate, insoluble in alkalis, soluble in acids and ammonia solutions with formation of colourless complex of tetraammin-cadmium-ion:

    CdCl2 + 2NH4OH = Cd(OH)2+ 2NH4Cl Cd(OH)2 + 4NH3 = [Cd(NH3)4](OH)2

    2. Action of sodium sulphide. Hydrogen sulphide or sulphides of alkaline metals at ~ 0,5 with cadmium ions form yellow precipitate, insoluble in solution of sodium sulphide and sodium hydroxide, soluble in concentrated chloride and nitrate acids:

    CdCl2 + H2S = CdS + 2HCl CdS + 4HCl = H2[CdCl4] + H2S

    CdS + 4HNO3 = Cd(NO3)2 + S + 2NO2 + 2H2O CdS + H2SO4 = CdSO4 + H2S

    3. Action of sodium hydrogen phosphate. Sodium hydrogen phosphate forms white precipitate, soluble in acetic and mineral acids:

    3Cd(NO3)2 + 4Na2HPO4 = Cd3(PO4)2 + 2NaH2PO4 + 6NaNO3

    4. Action of ammoniumperchlorate. Ammonium perchlorate in ammonium solutions of cadmium salts forms white precipitate:

    Cd(NO3)2 + 2NH4ClO4 + 4NH3 = Cd[(NH3)4](ClO4)2 + 2NH4NO3

    5. Action of dithizone. Dithizone interacts with cadmium ions in interval p 6,5-14 with formation of red inner-complex compound, which can be extracted by chloroform or carbon tetrachloride:

    N

    NH

    NC S SCd

    N N

    NH

    N

    N

    C + 2HNO3

    NH

    N N

    NC SH2 + Cd(NO3)2

  • Cations reactions 29

    Reactions of cobalt(II) cations detection:

    1. Action of ammonium hydroxide. Ammonium hydroxide precipitates from solutions of cobalt salts dark blue precipitate of basic salt, soluble in the reagent surplus with formation of yellow complex of hexaamminecobalt():

    CoCl2 + NH3 + H2O = CoOHCl + NH4Cl CoOHCl + NH3 + NH4Cl = Co[(NH3)6]Cl2 +H2O

    The chloride of hexaamminecobalt() under act of air oxygen gradually passes to the chloride of pentaamminecobalt() Co[(NH3)5Cl]Cl2 red colour. This reaction passes instantly under act of H2O2.

    2. Action of sodium hydroxide. The alkalis form with the cobalt() ions dark blue precipitate of basic salt CoOHCl:

    CoCl2 + NO = CoOHCl + NCl

    In case of further addition of alkali and heating the precipitate transforms to cobalt() hydroxide rose colour:

    CoCl + NO = Co(OH)2 + NCl

    On air Co(OH)2 precipitate gradually change colour to brown, transforming to cobalt(III) hydroxide.

    3. Action of sodium sulphide. Sulphides form black precipitate, soluble in mineral acids:

    CoCl2 + N2S = CoS + 2NCl

    4. Action of thiocyanates. Ammonium thiocynate in presence an amyl alcohol with the cobalt salts forms dark-blue complex, which passes to layer of organic solvent:

    CoCl2 + 4NH4SCN = (NH4)2[Co(SCN)4] + 2NH4Cl

    5. Action of ammonium tetrathiocyanomercurate(II). Ammonium tetrathiocyanomercurate(II) with the cobalt ions forms blue complex:

    2(NH4)2[Hg(SCN)4] + CoSO4 = Co[Hg(SCN)4] + 2(NH4)2SO4

    This reagent in presence of zinc salts forms double salt of cobalt-zinc tetrathiocyanomercurate(II) having navy colour:

    2(NH4)2[Hg(SCN)4] + CoSO4 + ZnSO4 = Zn[Hg(SCN)4]Co[Hg(SCN)4] + 2(NH4)2SO4

    6. Action of -nitroso--naphthole. -nitroso--naphthole with the cobalt() ions forms red-brown precipitate, soluble in organic solvents chloroform and benzene. The oxidization of cobalt() to cobalt() takes place in acidic environment under action of hydrogen peroxide:

    OHNO N-OH

    O

  • Cations reactions 30

    N

    O

    OCo

    NOO

    N

    O

    O

    CoCo

    N-OHO

    + Co(NO3)2 + H2O2 + HNO3 + 3HNO3 + 2H2O3

    7. Reaction of Rinmanns green formation. After burning a piece of filtration paper, moistened by solution of zinc and cobalt nitrate, get an ash, painted in green colour of cobalt zincate:

    Zn(NO3)2 + Co(NO3)2 = CoZnO2 + 4NO2 + O2

    Reactions of copper(II) cations detection:

    1. Action of ammonium hydroxide. At first ammonium hydroxide from solutions of copper() salts forms blue-green precipitate of basic salts of copper, which dissolves in the reagent surplus with formation of intensive navy complex:

    CuSO4 + 2NH4OH = (CuOH)2SO4 + (NH4)2SO4 (CuOH)2SO4 + (NH4)2SO4 +6NH3 = 2[Cu(NH3)4]SO4 + 2H2O

    In case of acidifying the ammonium complex of copper destroys as a result of exchange of ammonium molecules to + ions with formation of more stable NH4+ complex. The navy colour of solution thus changes on blue.

    2. Action to sodium hydroxide. Hydroxides of alkaline metals with copper() ions forms blue precipitate, which in case of heating loses water and transfers to black oxide:

    CuSO4 + 2NOH = Cu(OH)2 + 2N2SO4 Cu(OH)2 = CuO + 2O

    Cu(OH)2 soluble in the ammonia solutions and organic acids (tartaric, citric) with complexes formation. In concentrated solutions of alkalis Cu(OH)2 dissolves, forming cuprites Na2CuO2.

    3. Reducing reaction. The reaction of copper() ions reducing to elemental copper can be carried out by more active metals (iron, zinc, aluminium):

    CuSO4 + Zn = Cu + ZnSO4

    An acidified by sulphate or chloride acid solution of copper salt places on metallic plate. On the plate appears red spot of free copper.

  • Cations reactions 31

    4. Action of potassium hexacyanoferrate(). Potassium hexacyanoferrate() with the copper salts forms red-brown precipitate, insoluble in diluted acids:

    2CuSO4 + K4[Fe(CN)6] = u2[Fe(CN)6] + 2K2SO4

    5. Action of cuprone (benzoynoxime). Cuprone with the copper() ions forms insoluble dark-green complex:

    O NO

    CHCH

    Cu

    + H2SO4

    OH

    CH

    NOH

    CH + CuSO4

    6. Flame test. Salts of copper() paint colourless flame in dark blue or green colour.

    Reactions of nickel cations detection:

    1. Action of ammonium hydroxide. Ammonium hydroxide from solutions of nickel(II) salts precipitates green precipitate of basic salt of nickel(), soluble in surplus of reagent with formation of indigo blue complex:

    Ni(NO3)2 + NH3+ H2O = NiOHNO3 + NH4NO3 NiOHNO3 + NH4NO3 + 5NH3 = [Ni(NH3)6](NO3)2 + H2O

    2. Action of sodium hydroxide. Alkalis with nickel(II) ions form soluble in acids green precipitate:

    NiSO4 + 2NaOH = Ni(OH)2 + Na2SO4

    3. Action of sodium monhydrogenphosphate. Sodium hydrogenphosphate with nickel(II) cations forms green precipitate:

    3Ni(NO3)2 + 4Na2HPO4 = Ni3(PO4)2 + 2NaH2PO4 + 6NaNO3

    4. Action of diacetyl dioxime. Diacetyl dioxime with nickel ions forms inner-complex compound halving red colour:

    CH3

    CH3 NOH

    N-O

    CH3

    CH3N

    OH

    O-N C

    CC

    CNi + H2SO4

    CH3

    CH3 N-OH

    N-OHC

    C2 + NiSO4

    The reaction performs on filtration paper and uses for fractional method.

  • Cations reactions 32

    Reactions of mercury cations detection:

    1. Action of ammonium hydroxide. Ammonia solution from water solutions of mercury(II) salts precipitates white precipitate, soluble in the reagent surplus with formation of colourless complex:

    HgCl2 + 2NH3 = HgNH2Cl + NH4Cl HgNH2Cl + NH4Cl + 2NH3 = [Hg(NH3)4]Cl2

    2. Action of sodium hydroxide. Hydroxides of alkaline metals from water solutions of mercury(II) salts precipitate yellow precipitate:

    HgCl2 + 2NaOH = HgO + 2NaCl + H2O

    3. Action of iodides. Potassium iodide with mercury(II) cations forms brightly red precipitate, soluble in surplus of reagent with formation of the colourless complex:

    HgCl2 + 2KI = HgI2 + 2KCl HgI2 + 2KI = K2[HgI4]

    The reaction goes in weak acidic environment. The reaction with iodides uses for mercury(II) cations detection by drops technique in presence of all another cations: the red spot of HgI2 forms in the centre of filter paper.

    4. Action of sulphides. Solubility of sulphides. Sodium sulphide from solutions of mercury(II) salts precipitates brown-black precipitate:

    HgCl2 + Na2S = HgS + 2NaCl

    Precipitate is insoluble in chloride and nitrate acids, but soluble in mixture of this acids (aqua regia):

    3HgS + 2HNO3 + 12HCl = 3H2[HgCl4] + 3S + 2NO + 4H2O

    5. Action of reducers. Reducers (SnCl2, Cu) proceed mercury(II) cations to mercury() cations, and then to the free mercury. In solutions or on filtration paper in case of interaction of mercury salts with tin(II) chloride appears black precipitate of free mercury:

    HgCl2 + SnCl2 = Hg2Cl2 + SnCl4 Hg2Cl2 + SnCl2 = 2Hg + SnCl4

    If on copper plate to place a drop of mercury(II) salt solution, on plate through 4-5 min. will appear black precipitate of free mercury:

    HgCl2 + Cu = Hg + CuCl2

    In case of the spot rubbing a brilliant plaque of copper amalgam appears.

    6. Action of diphenylcarbaside. Diphenylcarbaside with mercury(II) salts in itrate acid environment forms dark blue or violet complex:

  • Cations reactions 33

    NH-NHC-OH

    NH-N

    NH-NH

    NH NC-O Hg

    NH-NH

    NHNO-C

    2 + Hg(NO3)2

    + 2HNO3