Dr. Jehad M DiabFaculty of pharmacyDamascus UniversityGravimetric Analysis‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬Pharma.analytical chemistry II
Gravimetric AnalysisGravimetry is the Quantitative measurement of theanalyte by weighing a pure solid form of theprecipit...
Electrogravimetric methods. analyte isprecipitated on cathode as metal or on anodeas metal oxide Dr.Jehad Diab‫اﻟﺗرﺳﯾب‬ ‫ط...
and washand calculateDry and igniteprecipitatingPrecipitation steps in gravimetryDr.Jehad Diab‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬ ‫ﻣراﺣل‬
Dr.Jehad Diab‫اﻟرواﺳب‬ ‫ﺧواص‬
Mechanisms of precipitation1.Saturation: the amount of salt dissolved ismaximum under certain condition of pressure andtem...
Dr.Jehad Diab
Dr.Jehad Diab
Particle size and filterabilityVon Weimarn described an equation that can controlthe particle size of ppt; named Von Weima...
Proportional to RSSInversely Proportional to RSSDr.Jehad Diab
pH control of precipitationCa2+ + C2O42-  CaC2O4 (s)H2C2O4  2 H+ + C2O42-Feeder Reaction:Dr.Jehad DiabWeak basic medium
10-6 - 10-4 mm10-1 – 10 mmDr.Jehad Diab
Primary adsorbed layerAgNO3 + NaCl →AgCl↓ + NaNO3reagent analyte(Secondaryadsorbedlayer)Dr.Jehad Diab
Dr.Jehad Diab-------------------------------------------------------------------------------------------------------------...
coagulationpeptizationDr.Jehad Diab
adsorbedadsorbedThe result is coagulation of colloidal precipitateof adsorbedDr.Jehad DiabColloids particles must collide ...
And coagulation of colloidal precipitate is resulted in.Dr.Jehad Diabincreasing electrolyte concentration (HNO3 for AgCl) ...
High Electrolyte Concentrationto Aid PrecipitationExcess charge on colloid creates ionicatmosphere around particleD.C. Har...
Dr.Jehad DiabWashing a colloid with water to remove excess counterion or trapped impurities can result in peptization.‫اﻟﺗ...
Use a volatile electrolyteDr.Jehad Diab
Digestion and aging,to reduce impurities present and largerparticles obtainedOr moreDr.Jehad Diab‫واﻟﺗﻌﺗﯾق‬ ‫اﻟﺗﮭﺿﯾم‬
Fig. 10.1. Ostwald ripening.During digestion at elevated temperature:Small particles tend to dissolve and reprecipitate on...
Dr.Jehad Diab‫اﻟﺑﻠورﯾﺔ‬ ‫اﻟرواﺳب‬-----------------------------------------------------------------------------------------...
(inclusion)Sources of Coprecipitation(trapped impurities)adsorption(interferences)Post precipitation ‫اﻟﺗﺎﻟﻲ‬ ‫:اﻟﺗرﺳﯾب‬ S...
adsorbedDr.Jehad Diab‫اﻟﺳطﺣﻲ‬ ‫اﻹﻣﺗزاز‬()lsilver and nitrate ions, soAgNO3 is coprecipitated with the AgCl.
Dr.Jehad Diab------------------------------------------------ ------------------------------------------------------------...
Dealing with surface adsorptionDr.Jehad Diab
Dealing with surface adsorptionDr.Jehad Diab-------------------------------------------------------------------
OcclusionDr.Jehad Diab‫اﻹﺣﺗﺑﺎس‬
OcclusionDr.Jehad Diab
OcclusionDr.Jehad Diab----------------------------------------------------------------------------------------------------...
dDetermination of NH4+ as NH4MgPO4 , K+ will cause a mixedcrystal containing KMgPO4(inclusion ‫)اﻹﺣﺗواء‬Dr.Jehad Diab
Dr.Jehad Diab-------------------------------------------------------------------------------------------------------------...
Homogeneous precipitation. The best precipitates are obtained withhomogeneous precipitation, in which theprecipitating re...
Methods have been worked out to generate avariety of precipitants, such as hydroxide, sulfide,sulfate, phosphate, oxalate...
3Preparation of NH4OH as precipitant by hydrolysis of ureaAl(OH)3,Fe(OH)3,Sn(OH)4,Bi(OH)3,Th(OH)4Dr.Jehad Diab∆
thioacetamide CH2·CS.NH2 + H20 → CH2·CO.NH2 + H2S Cd, Cu, Mo, Sburea (NH2)2CO + 3H20 → CO2 + 2NH4+ + 20H- AI, Bi, Ga, Fe, ...
Dr.Jehad Diab‫اﻟراﺳب‬ ‫ﺗﺟﻔﯾف‬--------------------------------------------------------
Dr.Jehad Diab
250 oC600 oCDr.Jehad Diab
Dr.Jehad Diab‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬ ‫ﻓﻲ‬ ‫اﻟﺣﺳﺎﺑﺎت‬-------------------------------------------------------
Dr.Jehad Diab
Dr.Jehad Diab
Gravimetric calculationsf.wt analyte(g/mol) a (mol analyte)gf = ------------------------- × ------------------------f.wt p...
 Cl2 → AgCl(s)GF=1/2 × Cl2 /AgCl = Cl2 / 2AgCl=35.5*2/2(108+35.5)= 0.25 AlCl3 → AgCl(s)GF=1/3 × AlCl3 / AgCl = AlCl3 / 3...
Problems: Calculate the mass of analyte interm of grams to each gram of ppt for thefollowing analytes:Analyte ppt P(31g) ...
Problem : Determine the gravimetricfactors in term of symbols for thedetermination of:AnalyteAnalyte pptppt G.F.G.F.CaCaOO...
Problem : Determine the gravimetric factors interm of symbols for the determination of:(a) Aluminum as its hydroxyquinolat...
Problem : Determine the gravimetric factors for thedetermination of:1. In -> In2O3 GF2. HgO -> Hg5(IO6)2 GF3. K3PO4 -> K2P...
Example: in an organic sample (0.352g) phosphorouswas dissolved and converted to Mg2P2O7 precipitate(0.223 g). Calculate t...
Example: When an sample of impure potassiumchloride (0.4500g) was dissolved in water andtreated with an excess of silver n...
Dr.Jehad Diab
Mainly Al and MgDr.Jehad Diab
Dr.Jehad DiabOrganic reagents
Table: some of inorganic precipitating agentsprecipitants analyte and (formed precipitate, weighed)* NH3(aq) Be (BeO),Al ...
Table: some of inorganic precipitating agentsprecipitants analyte ( formed precipitate, weighed)* BaCl2 SO42- (BaSO4)( N...
Mainly Mg and AL‫ﺟدول‬:‫اﻟﺗرﺳﯾب‬ ‫ﻋواﻣل‬ ‫ﺑﻌض‬‫اﻟﻌﺿوﯾﺔ‬Cs+Mn+ +nHR→ MRn + nH+M2+ +2HR →MR2 + 2H+2, Ag+ , Cu+M+ +NaR →MR + ...
Mn+ +nNH4R -> MRn + nNH4+M2+ +H2R →MR + 2H+An- + nRCl -> RnA + nClDr.Jehad Diab
Ca2+→ CaC2O4 → CaO
Dr.Jehad Diab
Dr.Jehad Diab
Dr.Jehad Diab‫اﻟﻛﮭرﺑﺎﺋﻲ‬ ‫اﻟوزﻧﻲ‬ ‫اﻟﻘﯾﺎس‬•used for electroplating, extraction and purification ofof the analyte
Dr.Jehad Diab
‫اﻟﺗﻔﻛك‬ ‫ﻛﻣون‬current-voltage relation for electrolysis .
Cu2+ +2e => CuAg(CN)2- + e => Ag +2CN-Pb2+ +2H2O => PbO2 + 4H+ +2eDr.Jehad Diab
Dr.Jehad Diab96500=1‫ﺑﺎﻟﻛوﻟوم‬ ‫وﯾﻘدر‬ ‫ﻓﺎراداي‬
CU2+Determine the number of grams of Cu2+ thatcould be deposited on cathode as Cu,if currentof 6 amperes is applied for 5 ...
Dr.Jehad Diab
Dr.Jehad Diab
RevisionDiminishing importance of gravimetry, as a resultof the development of much faster (though usuallyless precise) i...
We have emphasized the factors that facilitate theformation of coarse, pure, easily filterableprecipitates, explained why...
The EndDr.Jehad Diab
Gravimetric methods of analysis [compatibility mode]
Gravimetric methods of analysis [compatibility mode]
Gravimetric methods of analysis [compatibility mode]
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Gravimetric methods of analysis [compatibility mode]

  1. 1. Dr. Jehad M DiabFaculty of pharmacyDamascus UniversityGravimetric Analysis‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬Pharma.analytical chemistry II
  2. 2. Gravimetric AnalysisGravimetry is the Quantitative measurement of theanalyte by weighing a pure solid form of theprecipitate.Gravimetric Analysis is one of the most accurateand precise methods of macro-quantitative analysis.Often required for high precisionObtaining pure solids from solutions containingan unknown amount of a metal ion is done byprecipitation. Dr.Jehad Diab
  3. 3. Electrogravimetric methods. analyte isprecipitated on cathode as metal or on anodeas metal oxide Dr.Jehad Diab‫اﻟﺗرﺳﯾب‬ ‫طراﺋق‬‫اﻟﺗطﺎﯾر‬ ‫طراﺋق‬‫اﻟﻛﮭرﺑﺎﺋﻲ‬ ‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬ ‫طراﺋق‬
  4. 4. and washand calculateDry and igniteprecipitatingPrecipitation steps in gravimetryDr.Jehad Diab‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬ ‫ﻣراﺣل‬
  5. 5. Dr.Jehad Diab‫اﻟرواﺳب‬ ‫ﺧواص‬
  6. 6. Mechanisms of precipitation1.Saturation: the amount of salt dissolved ismaximum under certain condition of pressure andtemperature2.Supersaturation: the amount of salt is larger than atsaturation step, turbid solution3.nucleation: when a small number of ions ,atoms,molecules initially unite either spontaneous orinduced resulting in very small aggregates of asolid during precipitation.4.Particle growth: the three dimensional growth ofparticle nucleus converted into a larger crystalDr.Jehad Diab‫اﻟﺗرﺳﯾب‬ ‫آﻟﯾﺎت‬‫اﻹﺷﺑﺎع‬‫اﻹﺷﺑﺎع‬ ‫ﻓوق‬‫اﻟﺗﻧوي‬‫اﻟﺟزﯾﺊ‬ ‫اﻟﻧﻣو‬
  7. 7. Dr.Jehad Diab
  8. 8. Dr.Jehad Diab
  9. 9. Particle size and filterabilityVon Weimarn described an equation that can controlthe particle size of ppt; named Von Weimarn ratio• RSS= Q-S/S (Rss = Relative supersaturation, Q isconcentration of the solute at any instant. S is itsequilibrium solubility)Dr.Jehad Diab
  10. 10. Proportional to RSSInversely Proportional to RSSDr.Jehad Diab
  11. 11. pH control of precipitationCa2+ + C2O42-  CaC2O4 (s)H2C2O4  2 H+ + C2O42-Feeder Reaction:Dr.Jehad DiabWeak basic medium
  12. 12. 10-6 - 10-4 mm10-1 – 10 mmDr.Jehad Diab
  13. 13. Primary adsorbed layerAgNO3 + NaCl →AgCl↓ + NaNO3reagent analyte(Secondaryadsorbedlayer)Dr.Jehad Diab
  14. 14. Dr.Jehad Diab-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  15. 15. coagulationpeptizationDr.Jehad Diab
  16. 16. adsorbedadsorbedThe result is coagulation of colloidal precipitateof adsorbedDr.Jehad DiabColloids particles must collide with one another tocoalesce. However ,the negatively charged ionicatmospheres of particles repel one another. the particles,therefore ,must have enough kinetics energy to overcomeelectrostatic repulsion before the can coalesce. Heatpromotes coalescence by increasing the kinetic energy .And coagulation of colloidal precipitate is resulted in.
  17. 17. And coagulation of colloidal precipitate is resulted in.Dr.Jehad Diabincreasing electrolyte concentration (HNO3 for AgCl) decreasesthe volume of the ionic atmosphere and allows particles tocome closer together before electrostatic repulsion becomesignificant. For this reason .most gravimetric precipitations aredone in the presence of an electrolyte.
  18. 18. High Electrolyte Concentrationto Aid PrecipitationExcess charge on colloid creates ionicatmosphere around particleD.C. Harris, Quantitative Chemical Analysis, 6th Ed., p686
  19. 19. Dr.Jehad DiabWashing a colloid with water to remove excess counterion or trapped impurities can result in peptization.‫اﻟﺗﺷﺑﻐر‬ ‫او‬ ‫اﻟﺑﺑﺗزة‬ ‫ﻣﻌﺎﻟﺟﺔ‬
  20. 20. Use a volatile electrolyteDr.Jehad Diab
  21. 21. Digestion and aging,to reduce impurities present and largerparticles obtainedOr moreDr.Jehad Diab‫واﻟﺗﻌﺗﯾق‬ ‫اﻟﺗﮭﺿﯾم‬
  22. 22. Fig. 10.1. Ostwald ripening.During digestion at elevated temperature:Small particles tend to dissolve and reprecipitate on larger ones.Individual particles agglomerate.Adsorbed impurities tend to go into solution.During digestion at elevated temperature:Small particles tend to dissolve and reprecipitate on larger ones.Individual particles agglomerate.Adsorbed impurities tend to go into solution.©Gary Christian,Analytical Chemistry,6th Ed. (Wiley)‫اﺳﺗواﻟد‬ ‫ﻧﺿوج‬ ‫أو‬ ‫اﻟﺗﮭﺿﯾم‬
  23. 23. Dr.Jehad Diab‫اﻟﺑﻠورﯾﺔ‬ ‫اﻟرواﺳب‬------------------------------------------------------------------------------------------------------------------------------------------------------
  24. 24. (inclusion)Sources of Coprecipitation(trapped impurities)adsorption(interferences)Post precipitation ‫اﻟﺗﺎﻟﻲ‬ ‫:اﻟﺗرﺳﯾب‬ Sometimes a precipitate standingin contact with the mother liquor becomes contaminated by theprecipitation of an impurity on top of the desired precipitate.Dr.Jehad Diab‫اﻟﻣﺷﺗرك‬ ‫اﻟﺗرﺳﯾب‬‫اﻟﺳطﺣﻲ‬ ‫اﻹﻣﺗزاز‬‫اﻹﺣﺗﺑﺎس‬‫اﻹﺣﺗواء‬
  25. 25. adsorbedDr.Jehad Diab‫اﻟﺳطﺣﻲ‬ ‫اﻹﻣﺗزاز‬()lsilver and nitrate ions, soAgNO3 is coprecipitated with the AgCl.
  26. 26. Dr.Jehad Diab------------------------------------------------ -----------------------------------------------------------------------------------------------------------------------------------Coprecipitation error: negative or positive errorsEx: (a). in Cl analysis, colloidal AgCl + AgNO3 → (+) error(b). in Ba2+ → BaSO4 analysisif Ba(NO3)2 (larger FW than BaSO4) → (+) errorif BaCl2 ( FW: BaCl2 < BaSO4) → (-) error
  27. 27. Dealing with surface adsorptionDr.Jehad Diab
  28. 28. Dealing with surface adsorptionDr.Jehad Diab-------------------------------------------------------------------
  29. 29. OcclusionDr.Jehad Diab‫اﻹﺣﺗﺑﺎس‬
  30. 30. OcclusionDr.Jehad Diab
  31. 31. OcclusionDr.Jehad Diab----------------------------------------------------------------------------------------------------------------------------------------------------------------------
  32. 32. dDetermination of NH4+ as NH4MgPO4 , K+ will cause a mixedcrystal containing KMgPO4(inclusion ‫)اﻹﺣﺗواء‬Dr.Jehad Diab
  33. 33. Dr.Jehad Diab-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  34. 34. Homogeneous precipitation. The best precipitates are obtained withhomogeneous precipitation, in which theprecipitating reagent is gradually generated in thesample solution, through a slow chemical reaction. In this way there is never a large excess ofreagent, so that nucleation is slow, giving allexisting nuclei plenty of time to grow.The precipitating reagent is usually formed bythe slow hydrolysis of an organic compound atelevated temperature, but even synthesis ispossible, as in the generation of dimethylglyoximeDr.Jehad Diab‫اﻟﻣﺗﺟﺎﻧس‬ ‫اﻟﺗرﺳﯾب‬
  35. 35. Methods have been worked out to generate avariety of precipitants, such as hydroxide, sulfide,sulfate, phosphate, oxalate, 8-hydroxyquinoline,and chromate.Both the temperature and the pH must becontrolled, because both usually affect the rates ofthe hydrolysis reaction. Moreover, as we saw in thepH is often crucial in the formation of theprecipitate.Homogeneous precipitationDr.Jehad DiabSolid formed by homogeneous precipitation are generally purer and moreeasily filtered than precipitate generated by direct addition of a reagent tothe analyte solution.
  36. 36. 3Preparation of NH4OH as precipitant by hydrolysis of ureaAl(OH)3,Fe(OH)3,Sn(OH)4,Bi(OH)3,Th(OH)4Dr.Jehad Diab∆
  37. 37. thioacetamide CH2·CS.NH2 + H20 → CH2·CO.NH2 + H2S Cd, Cu, Mo, Sburea (NH2)2CO + 3H20 → CO2 + 2NH4+ + 20H- AI, Bi, Ga, Fe, Sn, ThSulfamic acid NH2S03H + H20 → NH4+ + H + + SO42+ Ba, Ca, Pb, SrTrimethyle phosphate (CH30)3PO + 3H20 → 3CH30H + 3H+ + PO43- ZrDimethyl oxalate CH30.CO.CO.OCH3 + 2H20 → 2CH30H + 2H + + C2042- Ca, Mg, Zn8-acetoxyquinoline + H20 → CH3C02H + 8-hydroxyquinoline AI, Mg, U, Zn2Cr3+ + BrO3- + 5H20 → Br- + l0H+ + 2CrO42- PbBiacetyl plus hydroxylamine CH3·CO.CO.CH3 + NH20H → dimethylglyoxime + 2H20 NiTable. Some common reactions for homogeneous precipitationreagent generating reaction used to precipitateDr.Jehad Diab
  38. 38. Dr.Jehad Diab‫اﻟراﺳب‬ ‫ﺗﺟﻔﯾف‬--------------------------------------------------------
  39. 39. Dr.Jehad Diab
  40. 40. 250 oC600 oCDr.Jehad Diab
  41. 41. Dr.Jehad Diab‫اﻟوزﻧﻲ‬ ‫اﻟﺗﺣﻠﯾل‬ ‫ﻓﻲ‬ ‫اﻟﺣﺳﺎﺑﺎت‬-------------------------------------------------------
  42. 42. Dr.Jehad Diab
  43. 43. Dr.Jehad Diab
  44. 44. Gravimetric calculationsf.wt analyte(g/mol) a (mol analyte)gf = ------------------------- × ------------------------f.wt ppt(g/mol) b(mol ppt)gf = g analyte / g pptg analyte = g ppt × gf% analyte =( g analyte / g sample) × 100% analyte = (g ppt × GF) / g sample) ×100% analyte = (g ppt × GF) / g sample) ×100Dr.Jehad Diab
  45. 45.  Cl2 → AgCl(s)GF=1/2 × Cl2 /AgCl = Cl2 / 2AgCl=35.5*2/2(108+35.5)= 0.25 AlCl3 → AgCl(s)GF=1/3 × AlCl3 / AgCl = AlCl3 / 3AgCl I → Hg5(IO6)2GF=2I/ Hg5(IO6)2Determine GF:Dr.Jehad Diab
  46. 46. Problems: Calculate the mass of analyte interm of grams to each gram of ppt for thefollowing analytes:Analyte ppt P(31g) → Ag3po4 (711g ) K2HPO4(136g) → Ag3po4 (711g ) Bi2S3 (514 g) → BaSO4 (233 g)g analyte = g ppt × gfg p =g Ag3PO4 ×GF= 1 ×31 / 711=0.044 g p/1g pptDr.Jehad Diab
  47. 47. Problem : Determine the gravimetricfactors in term of symbols for thedetermination of:AnalyteAnalyte pptppt G.F.G.F.CaCaOO CaCaCOCO33 CaOCaO/CaCO/CaCO33FeFeSS BaBaSSOO44 FeSFeS/BaSO/BaSO44UUOO22(NO(NO33))22 UU33OO88 33UOUO22(NO(NO33))22/U/U33OO88CrCr22OO33 AgAg22CrCrOO44 CrCr22OO33//22AgAg22CrOCrO44Dr.Jehad Diab
  48. 48. Problem : Determine the gravimetric factors interm of symbols for the determination of:(a) Aluminum as its hydroxyquinolate,AI(C9H60N)3 (Al AI(C9H60N)3)(b) Phosphorus as phosphomolybdic anhydride,P2Mo24078 (P P2Mo24078 )(c) Potassium as its chloroplatinateK → K2PtCl6(d) Sulfur as barium sulfate,( S → BaS04)(e) Nickel as nickel dimethylglyoxime,( Ni → Ni(C4H702N2)2Dr.Jehad Diab
  49. 49. Problem : Determine the gravimetric factors for thedetermination of:1. In -> In2O3 GF2. HgO -> Hg5(IO6)2 GF3. K3PO4 -> K2PtCl6 GF4. K3PO4 -> Mg2P2O7 GF5. AgIO3 -> Ba(IO3)2 GF6. AgNO3 -> AgIO3 GF7. (NH4)2SO4 -> BaSO4 GF8. Mn3O4 -> MnO2 GF9. Cu2HgI4 -> Cu GFCr -> Cr203 GFDr.Jehad Diab10.
  50. 50. Example: in an organic sample (0.352g) phosphorouswas dissolved and converted to Mg2P2O7 precipitate(0.223 g). Calculate the percentage %P in the originalsample.Dr.Jehad Diab2P(gfw 31 g) → Mg2P2O7 (gfw 222.6)GF=2× 31 /222.6 =0.2783% analyte =(g ppt × GF / g sample) × 100%P =( 0.223 × 0.2783 / 0.352) ×100 = 17.1 %
  51. 51. Example: When an sample of impure potassiumchloride (0.4500g) was dissolved in water andtreated with an excess of silver nitrate, 0.8402 g ofsilver chloride was precipitated. Calculate thepercentage KCl in the original sample.Answer:KCl ( gfw =74.50) => AgCl ( gfw =143.50)GF= 74.50/143.50=0.519%KCl = (mass of AgCl *GF/mass of KCl) *100==( 0.8402*0.519/0.4500 )*100 = 96.90%Dr.Jehad Diab
  52. 52. Dr.Jehad Diab
  53. 53. Mainly Al and MgDr.Jehad Diab
  54. 54. Dr.Jehad DiabOrganic reagents
  55. 55. Table: some of inorganic precipitating agentsprecipitants analyte and (formed precipitate, weighed)* NH3(aq) Be (BeO),Al (Al2O3),Cr(Cr2O3), Fe(Fe2O3)(NH4OH) Sn (SnO2),Zr (ZrO2) H2S Zn (ZnS→ZnO),As (As2S3 →As2O3 Or As2O5),Bi (Bi2S3 (NH4)2HPO4 Mg(Mg2P2o7),Zn(Zn2P2O7),Cd(Cd2P2O7) H2SO4 Sr,Cd,Pb,Ba (all as sulphate) H2PtCl6 K (K2PtCl6) HCl Ag (AgCl), Hg(Hg2Cl2)AgNO3 C l(AgCl), Br (AgBr), I (AgI)Dr.Jehad Diab
  56. 56. Table: some of inorganic precipitating agentsprecipitants analyte ( formed precipitate, weighed)* BaCl2 SO42- (BaSO4)( NH4)2S Hg (HgS) HNO3 Sn4+ (SnO2) H5IO6 Hg (Hg5(IO6)2 NaCl, Pb(NO3)2 F (PbClF) MgCl2,NH4Cl PO43- (Mg2P2O7)Ca2+ H2C2O4 CaCO3 or CaODr.Jehad Diab-------------------------------------------------------------------------------------------------------* After drying or ignitionFe3+ + OH-→Fe(OH)3 → Fe2O3weighed formppt
  57. 57. Mainly Mg and AL‫ﺟدول‬:‫اﻟﺗرﺳﯾب‬ ‫ﻋواﻣل‬ ‫ﺑﻌض‬‫اﻟﻌﺿوﯾﺔ‬Cs+Mn+ +nHR→ MRn + nH+M2+ +2HR →MR2 + 2H+2, Ag+ , Cu+M+ +NaR →MR + Na+Dr.Jehad Diabinterfere
  58. 58. Mn+ +nNH4R -> MRn + nNH4+M2+ +H2R →MR + 2H+An- + nRCl -> RnA + nClDr.Jehad Diab
  59. 59. Ca2+→ CaC2O4 → CaO
  60. 60. Dr.Jehad Diab
  61. 61. Dr.Jehad Diab
  62. 62. Dr.Jehad Diab‫اﻟﻛﮭرﺑﺎﺋﻲ‬ ‫اﻟوزﻧﻲ‬ ‫اﻟﻘﯾﺎس‬•used for electroplating, extraction and purification ofof the analyte
  63. 63. Dr.Jehad Diab
  64. 64. ‫اﻟﺗﻔﻛك‬ ‫ﻛﻣون‬current-voltage relation for electrolysis .
  65. 65. Cu2+ +2e => CuAg(CN)2- + e => Ag +2CN-Pb2+ +2H2O => PbO2 + 4H+ +2eDr.Jehad Diab
  66. 66. Dr.Jehad Diab96500=1‫ﺑﺎﻟﻛوﻟوم‬ ‫وﯾﻘدر‬ ‫ﻓﺎراداي‬
  67. 67. CU2+Determine the number of grams of Cu2+ thatcould be deposited on cathode as Cu,if currentof 6 amperes is applied for 5 minutesDr.Jehad Diab
  68. 68. Dr.Jehad Diab
  69. 69. Dr.Jehad Diab
  70. 70. RevisionDiminishing importance of gravimetry, as a resultof the development of much faster (though usuallyless precise) instrumental methods.Consequently, gravimetry is used only when itssuperior precision is really needed. In that case,great care must be exercised to avoidcoprecipitation of other sample components,occlusion of solvent in the precipitate, andadsorption of excess reagent, otherwise the extraeffort is negated by an impure or otherwise poorlydefined precipitateDr.Jehad Diab
  71. 71. We have emphasized the factors that facilitate theformation of coarse, pure, easily filterableprecipitates, explained why precipitates arepreferably generated homogeneously, and why theyare usually washed with electrolyte solutions ratherthan with water. Ammonium salts are often used for this purpose,because they will readily volatilize upon subsequentheating of the precipitate.Dr.Jehad Diab
  72. 72. The EndDr.Jehad Diab

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