INSTRUCTIONS MANUAL
CODE 80158.02
REV 0 02/10/09
(It can be modified without notice)
Page: 27
J.P. SELECTA s.a.
Ctra. NII Km 585.1 Abrera 08630 (Barcelona) España
Tel (34) 93 770 08 77 Fax (34) 93 770 23 62
e-mail: [email protected] - http://www.jpselecta.es
Determination:
5. Add 5.0 ml of potasic dichromat
and some glass ballons to regulate
ebullition to the sample and it is
homogenized carefully.
6. Add slowly 15 ml. of silver
suplhate - sulfuric acid, shaking
carefully the tube with a circular
movement, to cool down with cool
water of the tap or an ice bath, in
order to avoid any loss of organical
volatile substances.
7. Put the tubes dully prepared into
the stand tubes holder on their
support. With the help of a stand,
to introduce into the heating bloc.
8. Accoply on each tubes one
refrigerant in order to joint correctly
the polished gaskets.
9. Programm the temperature of
working (170-200ºC) and the time
of lenght (around 2 hours) of the
back flowing into the temperature
regulator and RAT time. Put the
selector of ramp (on the back pa-
nel of the unit RAT ) into the position
C.O.D.
10. Push on «START»and at this
moment the metallic bloc will hot
where the tubes are put. This will
be by a progressive way and when
it reaches the preselectionated
temperature, it will start to count
the time of back flowing.
11. After been finished the time of
back flowing, the heating in the
metallic bloc stops automatically
and you hear an acustic indicator.
At this moment, you should push
on «STOP» in order to finish the
process.
12- To let cool down the tubes for a
while and clean the projections that
have been produced in the inner wall
of the refrigerants into the recipient
of sample with a little volume of
distillated water.
13. To separe the refrigerants from
the tubes, and the tubes go outside
with the help of the stand , that is
put on the support. The sample is
dilued with 75 ml. of distillated water
and let cool down the ambien
temperature.
14. The excess of dichromat is
titred with iron sulphate (II) and of
amonium at the presence of 1 or 2
drops of ferroine . (It has to change
from green-blue colour to red
colour).
NOTES:
When the white is titred, you should
obtain a demand around 10 ml of
FAS.
When you titre the core test you
should obtain a demand of around
4.8ml of FAS.
Material:
C.O.D. equipment composed by:
- Metallic bloc heater.
- Temperature controler
- Tubes for digestion C.O.D.
- Stand for tubes holder.
- Refrigerants for C.O.D.
- Support for refrigerated tubes.
- Burette of precision for titration.
Sampling:
1- The samples for the laboratory
have to be collected preferably into
glass or polyethilene flasks. The
samples are analysed as soon as
possible, never more than 5 days
of their collection. If it is necessary
to conserve the samples before
making the tests, add 10 ml. of
sulfuric acid by 1 liter of sample and
to conserve between 0ºC and 5ºC.
The flasks are shaked and ensure
that the content is well
homogeneized before taking some
part of the test.
2. To introduce in the digestion tube
of D.C.O. 10,0 ml of the sample to
be analysed. If the value of the
D.C.O. of the sample is higher to
700 mg/l, this is made a dilution of
the original sample in order to obtain
a value of D.C.O. between 350 mg/
l and 700 mg/l.
Blank test:
3. A blank test is done at the same
tim e that the determ ination,
following the same operational
procedure, but instead using the
sam ple, you use 10 m l. of
distillated water.
The theoric demand of oxygen of
this solution is of 500 mg/l; the ex-
perimental procedure is satisfactory
if it is obtained at least 96 % of this
value.
CET ESSAI DEMANDE LA MANIPULATION DE SUBSTANCES DANGEREUSES
MANIPULATION OF CORROSIVE PRODUCTS IS REQUIRED
