Moisture Content in Graphite: Testing Methods and Standards
Representative Infinita Engineering Visual explaining the four-step workflow for Moisture Content Graphite.What Is ASTM C562?
ASTM C562 is the Standard Test Method for Moisture in a Graphite Sample. It provides a practical determination of the percentage of volatile moisture present in graphite due to adsorption of water vapor from the atmosphere — it does not determine moisture content in graphite exposed to liquid water.
Test Procedure
- Weigh a dried sample holder using an analytical balance
- Weigh the graphite sample separately
- Place the graphite in the sample holder and weigh both together (this becomes the initial combined weight)
- Heat the sample holder and graphite in a drying oven at 110C for 2 hours
- Remove from the oven and place in a desiccator to cool without reabsorbing atmospheric moisture
- Reweigh the sample holder and dried sample
- Calculate moisture content as the weight loss (initial combined weight minus dried combined weight) divided by the dry weight or total weight, expressed as a percentage
Sample Requirements
The standard sample should be a 6 x 6 inch (15 x 15 cm) square. The report includes at least two independent moisture determinations along with their average.
Related Method
ASTM C561 (Ash in a Graphite Sample) is a companion method that determines nonburnable residue content via ignition in a muffle furnace at 950C, and is often run alongside C562 as part of a broader graphite purity/quality characterization package.
Industry Specifications Referencing ASTM C562
- ASTM C561: ash content, commonly paired with moisture testing for graphite grade comparison
- Common applications: graphite electrodes, refractories, battery-grade graphite, lubricant-grade graphite
Also Read – Polymer Identification: FTIR, DSC & Spectroscopic Methods for Plastic ID
Conclusion
ASTM C562 is a simple gravimetric method, but its scope is narrow by design — it only captures atmospheric moisture adsorption, so graphite that has been exposed to liquid water needs a different characterization approach to get a representative moisture value.
Why is moisture content measured in graphite? Moisture testing determines how much water has been absorbed or retained by a graphite sample. Excess moisture can affect handling, weighing accuracy, processing, storage stability, and product consistency.
Which standard is used for graphite moisture testing? ASTM C562 is specifically used to determine moisture in graphite samples. It primarily measures volatile moisture absorbed from atmospheric humidity rather than water introduced through direct liquid contamination.
How is the oven-drying method performed? A known mass of graphite is heated under controlled conditions until the required drying period or constant mass is reached. The reduction in sample weight is calculated and reported as moisture content.
How is moisture content calculated? Moisture content is calculated by dividing the mass lost during drying by the original sample mass and multiplying the result by 100. It is generally reported as a percentage by weight.
Can Karl Fischer titration be used for graphite? Yes. Karl Fischer titration can be used when low-level or more selective water measurement is required. The graphite may require suitable extraction or oven-transfer conditions to release the moisture for analysis.
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