ANION ANALYSIS Flashcards
Describe the preparation of sodium carbonate extract.
To 0.5 g of sample , anhydrous sodium carbonate which is ten times its weight is added into a conical flask with a funnel at its mouth. To this 10 ml of distilled water is added and the mixture is boiled for 45 mins. The mixture is then centrifuged and the centrifugate is called the sodium carbonate extract.
Describe the test done for sulfide ion
To the SCE , a few drops of sodium nitroprusside solution (Na2[ Fe(CN)5NO]) were added. if violet coloration is observed then sulfide is confirmed.
Describe the test for sulfate ions.
To the SCE ( 5 drops), dil HCl is added until the effervescence stops. Then dil. HCl is added in excess with three drops. It was then placed on a hot water rack for 5 mins to expel CO2 and to this solution, 2-3 drops of BaCl2 is added. If white precipitate that is insoluble in conc. HCl and HNO3 are observed then sulfate is confirmed.
Describe the test done for nitrite ion.
SCE is acidified with acetic acid. Then sulphanilic acid and alpha-naphthalamine are added respectively. If bright red coloration of azo dye is observed then nitrite is confirmed.
Describe the test for nitrate if nitrite is not confirmed.
To the solution above , zinc dust is added and stirred. If nitrate is present , bright red coloration of azo dye is observed.
Describe the brown ring test for nitrate ion.
To 10-20 mg of sample , 0,5 ml of H2O is added. To this solution, 1 ml of conc. H2SO4 is added and stirred while cooling under a running tap. To this , freshly prepared FeSO4 solution is trickled down the test tube slowly and if a brown ring is observed at the junction of the two liquids then nitrate is confirmed.
What is the brown ring test unreliable for?
Presence of bromine,iodine,lead,barium,nitrite and iodate.
Give the test for chloride ion .
The SCE is acidified with dil. HNO3 . To this, a few drops of AgNO3 are added and a white precipitate of AgCl is observed. It is soluble in NH4OH.
Give the chromyl chloride test . What ion does it confirm?
To the sample , 3 times its weight of K2Cr2O7 is added in a dry test tube. to this conc. H2SO4 was added slowly and the mixture was heated gently . if red vapors of CrO2Cl2 are observed which on passing through dil. NaOH gives a yellow solution then chloride is confirmed.
explain the test for bromine and iodine.
The SCE is acidified with dil. HNO3 . To this, a few drops of AgNO3 are added, if a yellow precipitate that is soluble in NH4OH is observed then either bromine or iodine could be present.
Give the individual observations for bromine and iodine.
The SCE is acidified with dil. HCl and to this 1 ml of CCl4 solution and Cl2 water are added. The mixture was shaken vigorously. If a reddish-brown CCl4 layer is observed then bromine is confirmed . If a violet CCl4 layer is observed which disappears on excess Cl2 water then iodine is confirmed.
Describe the test for iodate.
The SCE was acidified with dil. CH3COOH.To this NH4SCN and CCL4 are added and shaken . If the layer of CCL4 becomes pink then iodate is confirmed.
Describe the test for bromate.
The SCE is acidified with dil. H2SO4. to this few drops of MnSO4 solution are added and heated for 2-3 mins. it is then cooled and then a few drops of benzidine reagent and crystals of sodium acetate are added. If blue coloration is observed then bromate is confirmed.
Give the confirmatory test for acetate.
SCE acidified with conc. H2SO4. To this few drops of ethyl alcohol are added and the mixture is gently warmed for 2-3 mins. it is then poured into a beaker with water. If the pleasant fruity smell is observed then acetate is present.
Give the test for interfering radical (PO43-)
The sample is heated with conc. HNO3 , cooled , centrifuged and only the centrifugate is treated with excess ammonium molybdate solution. If yellow precipitate which is soluble in NH4OH is observed then phosphate is confirmed.
