This is the method adopted by our Examination Department for moisture, volatile, ash and fixed carbon of flake graphite.

2. General Rules

1) Sampling method is in accordance with GB/T 3518 and GB/T 3519, and the sample in plastic bags or airproof bottles should be more than 50g.

2) Except for moisture analysis, the sample should be baked first at 105-110℃ to constant weight.

3) For high, medium and low carbon graphite, weight of sample should be exacted to 0.1mg.  When constant weight is required, the difference between two weighings should be less than 0.3mg.  For high purity graphite, the weight of sample should be exacted to 0.02mg.  When constant weight is required, the difference between to weighings should be less than 0.05mg.

4) Parallel tests should be conducted for each analysis item.

5) Testing results should be rounded to 3 decimal points for high purity graphite, 2 decimal points for all other analysis items.

3. Method for Moisture Analysis

1) Equipment

A. Oven at working temperature between 105 and 110℃

B. Measuring balance, accurate to 0.1mg

C. Weighing bottle

D. De-moisturizer

2) Analysis Procedure

Weigh 1-2g of un-dried sample and pour it into the weighing bottle, which is baked to constant weight, and place the same into the oven at 105-110℃.  Open the lid, and bake for 1 to 2 hours.  Then take the bottle out, close the lid, and place it into the de-moisturizer, cool it to room temperature and weigh.  Now put it back into the oven to bake for 30 minutes, take it out, cool it and weigh.  Repeat the same until the sample is baked to constant weight.  The last reading counts as final.

3) Calculation 

 X₁=(m₀-m₀)/m₀*100%

     In the above formula

     X₁  ——  Percentage of Moisture (%)

     m₀    ——  Weight of sample before drying (g)

     m    ——  Weight of sample after drying (g)

4. Method for Volatile Analysis (by high temperature furnace)

1) Equipment

A. High temperature furnace: the highest temperature must be above 1000℃

B. Measuring balance, accurate up to 0.1mg

C. Double lid ceramic crucible

D. Crucible stool

E. De-moisturizer

2) Testing Procedure

A. Weigh accurately 1g of sample, spread it evenly on the bottom of the double lid ceramic crucible which has already been dried to constant weight.  Rest the crucible on the stool, and close both lids, place it into the high temperature furnace, and close the furnace door tightly.  Burning for the required time, then take it out rapidly, cool for 1-2 minutes, put into De-moisturizer to cool down to room temperature, and weigh.

B. Burning Time

a) For fixed carbon content of not less than 98%, burn sample for 1 hour at 400 ± 20℃

b) For fixed carbon content of less than 98%, burn sample for 7 minutes at 950 ± 20℃.  Begin time count when the crucible is placed into the high temperature furnace.  Testing result is invalid if the temperature fails to reach 950 ± 20℃ within 3 minutes.

3) Calculation

X₂=(m-m₁)/m*100%

     
     In the above formula:

    X₂  ——  Percentage of Volatile (%)

    m    ——  Weight of dry sample before burning (g) 

   m₁   ——  Weight of sample after burning (g)

5. Method for Ash analysis

1) Equipment

A. High temperature furnace, the highest temperature must be above 1000℃

B. Measuring balance, accurate up to 0.1mg and 0.01mg

C. Square porcelain boat

D. De-moisturizer

2)  Testing Procedure

Weigh 0.3-1g sample (1-2g sample for high purity graphite), put the sample in the square porcelain boat which has already been dried to constant weight.  Place the square porcelain boat into the high temperature furnace to heat up to 900-1000℃ for 1 minute, then push it to the high temperature zone.  Keep the furnace door ajar so as to allow oxidation.  Keep burning until no black spot remains, take out, cool and weigh.  Repeat until the sample is burned to constant weight.

3) Calculation

    X₃=m₂/m*100%

        In the above formula:

        X₃   ——  Percentage of Ash (%)

        m    ——  Weight of dry sample before burning (g)

        m₂  ——  Weight of sample after burning (g)

6. Method for Fixed Carbon Analysis

1) For high, medium and low carbon graphite

     X₄=100%-X₂-X₃

         In the above formula: 
         X₄    ——  Percentage of fixed carbon (%)

         X₂   ——  Percentage of volatile (%)

         X₃   ——  Percentage of ash (%)

2) High purity praphite

        X₅=100%-X₃

         In above formula:
         X₅    ——  Percentage of fixed carbon (%)
         X₃    ——  Percentage of ash (%)

7.      Allowed Error
Allowed error between results of two parallel tests must match the requirements in the table below, and arithmetic average of the two results is the final result. Otherwise, sample and test again.