Non – Aqueous Titration & KJELDAHL Method Flashcards
3 reason why Non – Aqueous Titration use
- Most organic acids and bases are insoluble in water
❖ Most organic acids and bases are weak acids and bases
❖ Moisture must be avoided or at least limited to 0.05%
Non – Aqueous Titration: Acid titrant
Perchloric acid in glacial acetic acid or dioxane
Non – Aqueous Titration: Base titrant
Sodium methoxide,
Lithium methoxide in
ethylenediamine, n-butylamine, morpholine
Non – Aqueous Titration: Indicators
ACIDIMETRY - Weak bases
common: Crystal violet
malachite green,
quinaldine red,
methylrosaniline
Non – Aqueous Titration: Indicators
ACIDIMETRY - (relatively stronger base)
Methyl orange, methyl red, Thymol blue
Non – Aqueous Titration: Indicators
ALKALIMETRY - (weak acids)
Azoviolet
Non – Aqueous Titration: Indicators
ALKALIMETRY - (strong acids)
Thymol blue
Non – Aqueous Titration: Indicators
ALKALIMETRY - (most preferred)
potentiometric methods
A method designed to determine and quantify ammonia in
ammonium sulfate obtained by decomposing organic
substance with sulfuric acid
Nitrogen determination
KJELDAHL Method
Standardization in Non-aqueous titration: __________ + Perchloric acid —->__________+_______
1: Potassium Hydrogen Phthalate
2: Phthalic acid
3: Potassium Chlorate
KJELDAHL Method: standard sol- H2SO4
Sx + H2SO4 (CUSO4, Se) —> (NH4)SO4 + H2O
formation of Ammonium Sulfate
What step is this ?
Step 1: Digestion
KJELDAHL Method: standard sol- NaOH
(NH4)SO4 + NaOH—> NH3 + Na2SO4 + H2O
formation of Ammonia
What step is this?
Step 2: Neutralization
KJELDAHL Method: standard sol- H3BO3 (boric acid)
NH3 + H3BO3—–> (NH4)2B4O7+H2O
formation of Diammonium Tetraborate
What step is this?
Step 3: Distillation
KJELDAHL Method: standard sol- HCl
(NH4)2B4O7+HCl —-> (NH4)Cl + H3BO3
formation of Ammonium chloride
What step is this?
Step 4: Titration
if N is as NO3, _______ is add
salicylic acid
- USP Methods
- Method I for ________
- Method II for _______
macroanalysis (1)
semimicroanalysis (2)
Kjeldahl set-up
heater
Digestion flask (step 1)
Trap [digestion of sample nitrogen converted to ammonia]
Condenser [Distillation of ammonia into a trapping solution]
trapping flask [quantification of the ammonia by titration w/ a standard solution]
% sample = (ml x N) acid - (ml x N) base x meq sample
—————————————— x 100
wt of sample
formula for – Acidimetric assay, Nitrogen determination
Nitrogen determination use in ?
Protein in food, fertilizer, blood, assays of Heparin,
insulin, urea, povidone
Urea properties:
CO(NH2)2
60.06 g/mol
factor : 2
Precipitation Method is Also called?
Argentometric titration
Volumetric methods based on
reactions that yield ionic
compounds of limited
solubility
Argentometric titration
primary analyte use to find Argentometric titration is ???
Chlorine/ Halides
Common titrant use in Argentometric titration?
Silver Nitrate
other name of Silver Nitrate
AgNO3
Lapiz infernulariz
indelible ink
caustic pencil
Lunar pencil
Old medical use of silver nitrate?
neonatal conjunctivitis
recent treatment for neonatal conjunctivitis?
crede’s prophylaxis
crede’s prophylaxis is a combination of what drug?
Erythromycin + Tetracycline
neonatal conjunctivitis is caused by what kind of bacteria?
Neisseria Gonorrhea
3 ADSORPTION INIDICATOR
DCF: Dichlorofluorescein
Eosin Y: Tetrabromofluorescein
TEE: tetrabromophenolphthalein ethyl
types of indicator: takes part in chemical reaction ?
and commonly use in precipitation
Internal indicator
types of indicator: did not take part in the chemical reaction
and commonly use in neutralization
External Indicator
what indicator is use in redox method ex: KMnO4
self indicating indicator
formation of insoluble colored complex
slight excess thiocyanate ion
reacts with ferric ion from
the indicator producing a
faint reddish brown
coloration
- use HNO3 to acidify the analyte
Volhard Method
Volhard Method: Volumetric precipitation table
1st std : Silver nitrate
VS (2nd std): ammonium thiocyanate
indicator: Ferric Alum -(Fe(NH4)(SO4)2
example: Aminophylline NaCl
end point: faint reddish brown
FeNH4(SO4)2+ 3NH4SCN
Fe(SCN)3 ↓+ 2(NH4)2S
Formation of 2nd precipitate
chromate reacts with excess
silver ions forming a
secondary precipitate of
reddish silver chromate
INC Base of the analyte it use “ CaCO3 and NaHCO3”
INC Acid of the analyte it use CH3COOH
Mohr Method
Mohr Method: Volumetric precipitation table
1st std : Sodium Chloride (NaCl)
VS (2nd std): Silver nitrate
indicator: Potassium chromate (K2CrO)
example: SLS
end point:
reddish silver chromate
AgNO3 + K2CrO4 à AgCrO4 ↓+
KNO
COLORED ADSORPTION PRODUCT
change in color precipitate.
used as indicator in the titration of
potassium chloride with standard silver
nitrate solution.
❖ silver chloride (ppt)formed is
negatively charged due to adsorbed
chloride ion and the indicator exists in
the solution with a greenish yellow
❖ Direct titration with silver nitrate solution
slight excess of silver ion is adsorbed by the silver chloride
precipitate colloid particles became positively charged which
adsorb the fluoresceinate ions forming a reddish pink
adsorption product
Fajan Method
Fajan Method: Volumetric precipitation table
1st std : Sodium Chloride (NaCl)
VS (2nd std): Silver nitrate
indicator: DCF, Eosin Y, TEE
example: Phenylephrine HCl and Tubocuraine
end point:
reddish pink
Gay-Lussac: Volumetric precipitation table
1st std : Sodium Chloride (NaCl)
VS (2nd std): Silver nitrate
indicator: None
example: NaCl
cessation of precipitation
Liebig: Volumetric precipitation table
1st std : potassium biphthalate
VS (2nd std): Sodium tetraphenyl Boron
indicator: Bromophenol blue
example: Organic N Compounds
appearance of turbidity.
neonatal conjunctivitis is also called ?
ophthalmia neonatorum
USP requirements of Ammonium Bromide?
99.5% - 100.5%
USP requirements of Zinc Oxide?
95% - 98%
USP requirements of acetic acid?
2%-5%
factor of AgBr, KBr, BaCl2, Hg?
AgBr: 1
KBr: 1
BaCl2: 2
Hg: 2
Substances assayed: mainly used for determination of
__________and some compounds
that form insoluble products (ppt) with AgNO3
halides (Cl-, Br- & I-),
SCN-(thiocyanate),
CN- Cyanide
Heavy Metals: Hg
Primary standard of Precipitation Assay?
sodium chloride
Standardization of ____Silver nitrate
(concentration)
0.1 Normality
