Loss-on-Ignition Protocol (V. 1.2)
University of Cambridge
Department of Geography
Physical Geography
Laboratories
Equipment

Balance - 2 or 3 decimal place, eg. in 1g, 10% accuracy = 0.1g, 1% accuracy = 0.01g,
0.1% accuracy = 0.001g

Crucibles of an appropriate size for the samples - differently numbered

Desiccator - with purple silica gel, if white put in 105oC oven for 6 hours to dry out.

Drying oven - Must be booked in advance!

Heat proof gloves.

Muffle Furnace - capable of up to 1000oC - Must be booked in advance!

Tongs.

Trays & stack - capable of withstanding 1000oC.

Volumetric Sampler.
If you have large batches of samples, using a Sartorius balance connected to a pc is a useful way
to speed up collection of data.
Protocol (%water, bulk density, %organic, %calcium carbonate, %silicate residue)

Clean dry, numbered porcelain crucibles are weighed empty.

Approximately 1g of wet sediment is placed in the crucible, and the wet weight recorded.
If bulk density of the sample is required a calibrated 1 cm3 brass volumetric sampler
should be used and the sample should be weighed, allowing mass per unit volume to be
calculated.

Crucibles should then be placed on trays, the tray rack may be required if large numbers
of samples are being processed.

The samples are dried for 6 hours (until constant weight is achieved) usually overnight at
105oC in either the Drying Oven or Muffle Furnace. Remove trays carefully using the
heat proof gloves. Use tongs to place crucibles in desiccator until they reach a
temperature at which they can be handled safely. The desicator prevents the absorption of
water from the atmosphere and therefore weight gain. Then weigh samples again.

The samples are transferred to a muffle furnace then heated to 550oC for at least six hours
(overnight), the furnace should then be reduced to ~100oC, when this temperature has
been reached samples should be allowed to cool in a desiccator to a temperature at which
they can be safely handled, then weighed.

The samples are then returned to the furnace and heated to 950oC for at least six hours
(overnight) the furnace should then be reduced to ~100oC, when this temperature has
been reached samples should be allowed to cool in a desiccator to a temperature at which
they can be safely handled, then weighed.
Results

The weight loss when the samples are dried at 105 oC (wet weight - dry weight)
represents of the amount of pore-water held within the sample. The percentage of water
should be expressed as a proportion of the wet weight. If the volume of the sample taken
is known then the "Bulk Density" can be calculated from this, expressed as weight of
sample per unit volume, e.g. g/cm3 (g cm-3).

The weight loss between 105 and 550oC as a percentage of the total original dry sample
weight is the % organic material. This probably also includes water loss from clay
minerals, this is likely to be a insignificant addition.

The weight loss between 550 and 950oC is representative of the amount of CO2 released
from the sample. This can be used to calculate the amount of CaCO3 present in the
sample by using the ratio between the molecular weights, expressed as a percentage of the
total original dry sample weight this is the % carbon.
Calculation (molecular weights in brackets)

Ca (40.08) + C (12.01) + O3 (3 x 16.00) = CaCO3 (100.09)

C (12.01) + O2 (2 x 16.00) = CO2 (44.01) Removed between 550 - 950 oC

Ca (40.08) + O (16.00) = CaO (56.08) Remains in sample

So to calculate the quantity of CaCO3 the weight of CO2 lost must be multiplied by a
factor to account for the CaO remaining in the sample.

CaCO3 (100.09) / CO2 (44.01) = 2.274

So the part of the sample that is represented by the CaO is 2.274 times that of the known
CO2.

So to calculate the quantity of CaCO3 in a sample the weight lost between 550 - 950 oC
must be multiplied by 2.274.

The weight of the residue remaining after 950oC, minus the adjustment for carbon, as a
percentage of the total original dry sample weight is expressed as the % silicate residue.
% Coal

When analysing samples for CCRU a slightly different method is used. The samples are
prepared as above, and dried at 105oC, but then heated to 400oC and 480oC instead of 550
and 950oC. This distinguishes between organic matter, and coal.