PURPOSE
To lay down the procedure for Loss on drying of the materials.
APPARATUS
Muffle furnace with temperature controller capable of achieving up to 800°C
Silica, Platinum, Porcelain or Quartz crucibles
Graduated pipette – 1ml
Bunsen Burner
Desiccator
Nickel tongs
REAGENTS
Sulphuric Acid: AR grade
PROCEDURE
- Ignite the crucible in a muffle furnace at 600 ± 50°C for 30 min. Allow to cool in a desiccator over silica gel or other suitable desiccants to ambient temperature and weigh accurately. Note down the weight in g as W1.
- Transfer the sample about 1.0 g or as specified, into the crucible and weigh accurately. Note down the weight of the crucible with a sample in g as W2.
- Moisten the sample with a small amount of Sulphuric acid (usually 1 ml), and heat gently over a Bunsen burner, at a temperature as low as practicable, until the sample is thoroughly charred.
- After cooling, moisten the residue with a small amount of Sulphuric acid (usually 1 ml) and heat gently until white fumes are no longer evolved.
- Ignite at 600 ± 50°C in the muffle furnace until the residue is completely incinerated.
- Allow the crucible to cool in a desiccator and weigh accurately. Note down the weight in g as W3.
- If the amount of the residue so obtained exceeds the limit specified; repeat the moistening with Sulphuric acid, heating, and ignition as before, until constant weight is attained or until the percentage of residue complies with the limit.
CALCULATION
W1 = Weight in g of empty crucible
W2 = Weight in g of the crucible with sample before ignition.
W3 = Weight in g of the crucible with the residue of the sample after ignition.
REFERENCES
USP
BP
EP
Note: Ensure that flames are not produced at any time during the procedure.
Tags
GTP
