D4006_9 (16e1)
0 (0 Likes / 0 Dislikes)
The precision of
this test method
can be affected by
water droplets adhering
to the surfaces in the
apparatus and therefore
not settling into the
water trap to be measured.
To minimize the
problem, all apparatus
must be chemically
cleaned at least daily
to remove surface
films and debris, which
hinder free drainage of
water in the test apparatus.
More frequent cleaning
is recommended
if the nature of the
samples being run
causes persistent contamination.
To determine water
on a volume basis,
proceed as indicated in
section 7.1.2.3 of the written
standard.
Add sufficient
xylene to the flask.
Make the total xylene
volume 400 milliliters.
To determine water
on a mass basis,
proceed as indicated
in section 7.1.2.4.
Add sufficient xylene to the
flask to make the total xylene
volume 400 milliliters.
A magnetic stirrer is
the most effective device
to reduce bumping.
Glass beads or other boiling
aids, although less effective,
have been found to be useful.
Assemble the apparatus
as shown in figure 1,
making sure all connections
are vapor and liquid-tight.
It is recommended that
glass joints not be greased.
Insert a drying tube containing
an indicating desiccant
into the end of the container
to prevent condensation
of atmospheric moisture
inside the condenser.
Circulate water between
20 and 25 degrees
Celsius through the
condenser jacket.
Apply heat to the flask.
The type of crude
oil being evaluated
can significantly alter
the boiling characteristics
of the crude solvent mixture.
Heat should be applied slowly
during the initial stages
of the distillation,
approximately 1/2 to 1 hour,
to prevent bumping and possible
loss of water from the system.
Condensate shall not proceed
higher than 3/4 of the distance
up the condenser inner
tube, point A in figure
1 of the written standard.
To facilitate
condenser washdown,
the condensate should be
held as close as possible
to the condenser outlet.
After the initial
heating, adjust the rate
of boiling so that the
condensate proceeds
no more than 3/4 of the distance
up the condenser inner tube.
Distillate should
discharge into the trap
at a rate of approximately
two to five drops per second.
Continue distillation
until no water
is visible in any part
of the apparatus--
except in the trap--
and the volume of
water in the trap
remains constant for
at least five minutes.
If there is a
persistent accumulation
of water droplets in the
condenser inner tube,
flush was xylene.
A jet spray washing tube--
see figure 2 of the written
standard-- or equivalent device
is recommended.
The addition of an
oil-soluble emulsion breaker
at a concentration of 1,000
PPM to the xylene wash
helps dislodge the
clinging water drops.
After flushing, re-distill
for at least five minutes.
The heat must be shut off
at least 15 minutes prior
to washdown to prevent bumping.
After washdown, apply heat
slowly to prevent bumping.
Repeat this procedure
and no water
is visible in the
condenser and the volume
of the water in the trap
remains constant for at least
five minutes.
If this procedure does
not dislodge the water,
use the TFE
fluorocarbon scraper--
pick shown in figure 2
of the written standard--
or equivalent device to cause
the water to run into the trap.
When the carryover
of water is complete,
allow the trap and contents
to cool to 20 degrees Celsius.
Dislodge any drops
of water adhering
to the sides of the trap with
the TFE fluorocarbon scraper
or pick, and transfer
them to the water layer.
Read the volume of
the water in the trap.
The trap is graduated in
0.05-milliliter increments,
but the volume is estimated to
the nearest 0.025 milliliters.