ASTM C562 is used to determine the amount of volatile moisture present on graphite due to adsorption from the atmosphere. It cannot determine the amount of moisture in graphite exposed to liquid water. Values are presented in SI units.
Apparatus in ASTM C518 include a sample holder, an analytical balance, a drying oven, and a desiccator.
First, a dried sample holder is weighed with an analytical balance. Then, the graphite sample is weighed. After that, the graphite is placed in the sample holder and both are reweighed together.
After reweighing, the sample holder containing the graphite sample is heated in a drying oven at 110 °C for 2 hours. After that, the sample is removed from the oven and placed in the desiccator. When the graphite sample reaches room temperature, It is picked up from the desiccator and re-weighed.
The amount of moisture that was present in the graphite is calculated by subtracting the dry weight from the initial weight, and the moisture content is then calculated as the amount of water divided by the dry weight or total weight.
The sample should be a square of 6 × 6 inches (15 × 15 cm).
The percentage of moisture in the graphite sample is calculated as follows:
Moisture % = [(B – C) ÷ (B – A)] × 100
A = weight of sample holder,
B = weight of sample holder and sample, and C = weight of sample holder and dried sample.
The report includes at least two moisture determinations and their average.