EXPERIMENT 1
AIM: To separate green leaf pigments ( spinach leaves ) by TLC.
Requirements: Glass plate, silica gel ethanol and chloroform, spinach extract.
Theory: Spinach extract has chlorophyll and carotenoid hydrocarbons as the main
cstituents. The carotenoid hydrocarbons are non polar and weakly absorbed by
alumina and readily eluted wiyh hydrocarbon solvents.
PROCEDURE: Extraction of Spinach:
Take 70 g of spinach and crush it with 60 ml methano in mortar. Filter the
contents of mortar. Reject the filtrate. Reground the mixture with mixture of 30;40
methanol: petroleum ether .Filter the contents of mortar through cotton wool.
Preserve the filtrate and mark it as A . Reground the residue again and agin filter
and separate. Wash the petroleum ether layer twice with water to remove any
dissolved metahanol.
Seperation of Green leaf Pigments:
Prepare the TLC plate using silica gel as adsorbent. Spot the extract on plate at one
end and develop the chromatogram using 3% ethanol chloroform mixture as
solvent. The carotenes (orange to orange yellow spot),chlorophyll ( green to blue
green), xanthophylls(yellow) appear as spots. Mark the outer edge of each spot
carefully. Calculate the Rf value
Rf = Distance travelled by component/ Distance travelled by
solvent front
EXPERIMENT 2
AIM: To determine the percentage of acetic acid in a sample of commercial
vinegar.
Requirements: 0.1N NaOH, 0.1 N oxalic acid, given vinegar solution.
THEORY: Fixed amount of vinegar is titrated against standard sod.hydroxide
solution using phenolphthalein as indicator. Normality of acetic acid in vinegar is
then determined using normality equation.
PROCEDURE:
1. Prepare 0.1 N oxalic acid solution 1.575g in 250 ml water.
2. Prepare 0.1 N NaOH by dissolving 1.25 g in 250 ml water.
3. Standardization of NaOH solution: Pipette out 20 ml of NaOH in
flask.Add to it few drops of phenolphthalein indicator. Take oxalic acid in
burette. Run in acid until solution becomes colorless. Repeat such titrations
to get three concordant readings.
4. Titration of vinegar against standardized NaOH: Transfer vinegar solution
in burette. Pipette out 20 ml of standardized NaOH solution in flask and
also add 2-3 drops of phenolpkthalein as indicator. Titrate till solution
becomes colorless. Repeat the titration to get three concordant readings.
OBSERVATIONS AND CALCULATIONS:
Vol. of NaOH taken in titration flask = 20 ml
Normality of oxalic acid = 0.1 N
Applying normality equation ,
N1V1( NaOH) = N2V2 ( oxalic acid)
N1. 20
=
0.1 . V2( vol. of oxalic acid)
N1 = 0.1 . V1 / 20 = say x
TITRATION II
Percentage of acetic acid in vinegar
N3V3(acetic acid) = N4V4 ( NaOH)
N3 = 20. X/V3( vol. of acetic acid)
N3 = say y
Strength of acetic acid in vinegar = Eq. wt. .normality= 60 . y g/lt
% of acetic acid in vinegar = 60 .y.100/1000 g/ 100 ml
EXPERIMENT 3
AIM: Determine Gravimetrically the % of nickel in given salt as Ni(DMG)2
REQUIREMENTS: 1.0 % alc solution of DMG, given nickel sample.
THEORY: Nickel is estimated by precipitating it as nickel dimethyl glyoxime
complex when a solution of nickel salt is treated with an alcoholic solution of
DMG solution.
PROCEDURE:
1. Pipette out 20 ml of given solution into 400ml beaker provided with a
watch glass cover and stirring rod.
2. Add 1-2 ml of conc.HCl and dil. It to 200ml
3. Heat the solution to 70-80 degrees and add slight excess of 1%
alc,solution of DMG reagent.
4. Add immediately ammonia solution dropwise directly to the solution till
the pptn is complete. Then add little excess of ammonia.
5. Allow the beaker to stand on water bath for 20-30 miN.
6. Filter the cold solution through a sintered glass crucible which has been
heated to 110-120 degrees.
7. Wash the ppt with cold water several times till free bfrom chloride ions.
8. Dry the crucible at 110-120 degrees for 45 min in hot air oven.
9. Cool in a dessicator and weigh until constant weight is obtained.
CALCULATIONS:
Amt. of Nickel ammonium sulphate per litre = 20 g per litre
Vol. of sol. Taken for pptn = 20 ml
Constant wt . of crucible = a g
Constant wt of crucible+ nickel cpd. Residue= b g
Wt of residue = b-a = w g
20 ml of solution gives ppt = wg
1000 ml solution gives ppt = 1000.w/20= 50 w g
Now, Ni (58.7)=Ni(dmg)2 ( 288.7)
At.Wt. Ni / Mol wt. of salt complex= Strength of Ni/ Strength of salt complex
Strength of Ni = 58.7. 50 w/288.7 = x g/lt
Strength of salt = 20 g / lt
Strength of Nickel = Xg/ lt
% of nickel = x/20 . 100
Aim- 1. Determine the amount of calcium and magnesium present in the given
sample of water.
2. Total hardness of calcium and magnesium ions in the given sample.
Provided- 0.01M EDTA.
Theory- The solution is first titrated against EDTA solution using Erichrome black
T as indicator. This gives the total amount of calcium and magnesium present in
the sample.
This solution is again titrated against EDTA solution using calcon as indicator. The
second titration is conducted in the presence of high concentration of sodium
hydroxide which precipitate out magnesium as magnesium hydroxide. Thus in the
second titration only calcium reacts with EDTA solution. This titration gives the
amount of calcium in the solution. The difference between the first and the second
titration gives the magnesium content present in water.
For finding out the total hardness of water the total molarity of calcium and
magnesium ions in the water.
Procedure1. Take EDTA solution in the burette.
2. 2. Pipette out 20ml of the mixture solution in a conical flask. Dilute the
solution to about 50ml with 20-30ml of distilled water.
3. Add 5ml Of NH4Cl and NH4OH buffer solution. Add 3 to 4 drops of erio
chromic Black T indicator and heat the solution to 60oC
4. Run EDTA solution from the burette into the titration flask gradually until
the colour of the solution changes from wine red to pure blue.
5. Repeat the titratiom till atleast three reading.
Second titration
1. Pipette out 20 ml mix sol into a 250ml titration flask. Dilute the sol to
about 50ml with 20-30ml of distilled water.
2. Add 3-4ml of 50%sodium hydroxide sol when a white ppt’s of Mg(OH) 2
appears. shake it.add 2-3 drops of calcon indicator.
3. Run the EDTA sol from the burette dropwise and with continuous stirring
of the contents of the titration flask
4.Continue adding EDTA sol slowly until a blue color appears this is the end
point.
5.Repeat the titration until at least three readings.
Observations and calculations
First titration
Volume of the mixture sol taken for titration=20ml
Molarity of EDTA solution =0.01
S.no.
Initial reading
Final Reading
Volume
EDTA used
Indicator and end point=eriochrome black t-wine red to black
Let 20ml of mixture requires Vml of EDTA solution.
M1V1 =M2V2
Mmixture = 0.01*V2/20
Of
Second Titration
Volume of mixture solution taken for titration =20ml
Molarity of EDTA solution=0.01M
S. No
Initial reading
MCa2+=0.01*Vs/25 =y
Final reading
Vol of EDTA