Study Set Content:
The indicators used for volumetric precipitation methods
● Ferric ammonium sulfate
● Potassium chromate TS
● Adsorption indicators:
○ Dichloro fluorescein (DCF)
○ Eosin Y
○ Tetra bromo phenolphthalein ethyl ester (TEE)
Involves a change of color on the surface of the
precipitate
Fajan method
Standard solution used
Silver Nitrate
Positive indicators:
Eosin, TEE, DCF
Negative indicators:
Rhodamine
Sample Assays:
Phenylephrine HCL, Tubocurarine
HCL, Meperidine HCL
Involves the formation of a soluble red complex.
Volhard Method
Ex. At the end point, the excess thiocyanate will react with FAS
forming a red complex (ferric thiocyanate)
Ex. At the end point, the excess thiocyanate will react with FAS
forming a red complex (ferric thiocyanate)
Standard solution:
Potassium thiocyanate
Indicator used:
Ferric ammonium sulfate (FAS)
Sample assays:
Aminophylline for Theophylline. Sodium
chloride, Dextrose and NaCl injection.
Involves the formation of a second precipitate which is of a different color
from the primary precipitate, but this second precipitate must be more
soluble than the first.
Mohr Method
Ex. When a chloride content will react to silver nitrate to form a white
precipitate, when the chloride is completely precipitated a drop of silver
nitrate in excess will react with the indicator (chromate ion), forming a
brownish red ppt.
Ex. When a chloride content will react to silver nitrate to form a white
precipitate, when the chloride is completely precipitated a drop of silver
nitrate in excess will react with the indicator (chromate ion), forming a
brownish red ppt.
Standard solution:
Silver Nitrate
Indicator used:
potassium chromate
Sample assays:
Sodium lauryl for chloride content.
Involves formation of a blue precipitate
Liebig Method
Standard solution
Sodium tetraphenyl boron
Indicator used:
Bromophenol blue
