D482_8 (13)
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Heat the evaporating
dish or crucible
that is to be used for the
test at 700 to 800 degrees
Celsius for a minimum
of 10 minutes.
Cool to room temperature
in a suitable container
and weigh to the
nearest 0.1 milligrams.
The container in which the
dish or crucible is cooled
can be a desiccator not
containing a desiccating agent.
In addition, all
weighings of the crucibles
should be performed as soon
as the crucibles have cooled.
If it should be necessary
that the crucibles remain
in the desiccator
for a longer period,
than all subsequent
weighings should
be made after allowing
the crucibles and contents
to remain in the desiccator
for the same length of time.
When the sample is
sufficiently mobile,
mix thoroughly before weighing.
The mixing is
necessary to distribute
catalyzed finds and other
particulate material
throughout the sample.
Satisfactory mixing
can usually be
achieved by 10 minutes of manual
shaking or 10 minutes using
a mechanical shaker.
Examine the sample
for homogeneity
before proceeding with section
8.3 of the written standard.
Continue mixing the sample,
if it is not homogeneous.
When it is evident that the
sample is not homogenized
after repeating mixings, or
there is a reasonable doubt,
a non-aerating, high-speed,
shear mixer can be used.
Such a device is described in
annex A1 of Test Methods D4928.
When the sample cannot be
satisfactorily homogenized,
reject the sample and
acquire a new sample.
When the sample is viscous
or solid at room temperature,
heat the container carefully
until the sample is entirely
liquid, and mix carefully.
An oven at an appropriate
temperature can be used.
The sample can contain water.
After heating in
an oven, the water
can boil, causing
splattering or foaming.
The operator shall proceed
cautiously with the heating
step, wearing
appropriate personnel
protective equipment, such
as safety goggles and gloves.
Mixing this type of sample
shall be done carefully.
Stirring, rather than
shaking, in an option.
The quantity of test
specimen taken for testing
will depend upon the ash
content expected in the sample.
Refer to Table 1 of
the written standard.
The weighing procedure
will also depend upon
whether the sample
requires heating
or not, and whether more than
one portion has to be weighed.
Using a top-loading balance,
weigh into the dish or crucible
sufficient test specimen
to the nearest 0.1 grams
to yield no more than
20 milligrams of ash.
Determine the mass
of the test specimen
used in the analysis
at ambient temperature.
One way to do this is
to take the difference
between the initial
and final masses
of the sample container weighed
at ambient temperatures.
If one weighing is
sufficient, as determined
from Table 1 of the written
standard or experience,
proceed with steps
8.6 through 8.11.
If more than one addition of
test specimen is required,
proceed only through 8.6,
noting 8.6.1 and 8.7.
And allow the dish or crucible
to cool to ambient temperature
before adding more
sample as outlined
in 8.4 of the written standard.
Proceed with steps
8.6 through 8.11.
Carefully heat the
dish or crucible
with a Meker burner
or equivalent
until the contents can
be ignited by the flame.
Maintain the dish or crucible
at such a temperature
that the sample continues to
burn at a uniform and moderate
rate, leaving only a
carbonaceous residue when
the burning ceases.
A hotplate can be
used at this stage.
The test sample
may contain water
that can cause spattering.
The operator shall heat the
test portion cautiously,
while wearing
appropriate personnel
protective equipment, such
as safety goggles and gloves.
If spattering is very severe,
so that material escapes
the confines of the
dish or the crucible,
discard the test portion.
If the first test portion is
discarded, add 2 plus or minus
1 milliliters of
isopropyl alcohol--
warning, flammable--
to a second test
portion while stirring
with a glass rod
and warming the test portion
gently to liquefy it,
if it is solid or near solid.
Proceed as described in 8.6
of the written standard.
If this is unsuccessful,
repeat on a third test portion
using a 10 plus or minus
1 milliliter mixture of 50
plus or minus 5%
by volume toluene--
warning, flammable,
vapor harmful--
and 50 plus or minus 5% by
volume of isopropyl alcohol.
In either case,
any test specimen
that adheres to
the glass rod can
be returned to the dish using a
strip of ashless filter paper.
Continue burning as outlined
in 8.6 of the written standard.
Vigilance by the
operator is mandatory.
Burning samples shall
never be left unattended.
Some test specimens will
require extra heating
after the burning has ceased,
particularly heavy samples,
such as marine fuels,
which form crusts
over the unburned material.
The crust can be broken
with a glass rod.
Any crust that adheres
to the glass rod
can be returned to the dish
using a strip of ashless filter
paper.
Burn the remaining
test specimen.
The heavier material
tends to foam.
Therefore, the operator shall
exercise considerable care.
Overheating shall be avoided, so
that neither the test specimen
nor the dish are heated
to a red hot appearance,
as this can result
in loss of ash.
Likewise, the flame
shall never be
higher than the rim
of the dish to avoid
super heating the
crust, thereby producing
sparks that can result in
considerable loss of ash.
Heat the residue in the muffle
furnace at 775 plus or minus
25 degrees Celsius, until
all carbonaceous material
has disappeared.
Cool the dish to
room temperature
in a suitable container,
as referenced in Note 4
of the written standard,
and weigh to the nearest 0.1
milligrams.
Reheat the dish at 775 plus
or minus 25 degrees Celsius
for at least 20 minutes.
Cool in a suitable container
as referenced in Note 4
of the written
standard, and reweigh.
Repeat the heating, cooling,
and weighing process
until consecutive weighings
differ by not more than 0.5
milligrams.