Hanna Instruments HI934 Bedienungsanleitung Seite 112

3
DESCRIPTION
Method for the determination of bromine index of
bromine-reactive substances. This method typically
applies to aromatic hydrocarbons with only trace amounts
of olefins (alkenes) and having bromine indexes less than
1000. For samples with a bromine index greater than
1000, it is recommended to dilute the sample with a
suitable solvent. Results are expressed in
ELECTRODE
• HI76330 Dual Platinum Pin Electrode
• HI900517 Generator with Diaphragm
-or-
• HI900512 Generator without Diaphragm
REAGENTS
• Coulometric Bromine Index Reagent without Mercury
ACCESSORIES
• 1 mL syringe (clean and dry)
• 22-gauge, 6" non-coring septum penetration needle
(clean and dry)
• Solvent bottle, GL45 thread
REAGENT PREPARATION
• Prepare 200 mL of 119 g/L potassium bromide
solution, add 23.8 g of potassium bromide at a 200
mL volumetric flask, add roughly 125 mL of water,
shake until dissolved and bring to volume with
deionized or distilled water.
• To prepare 1 L of the reagent, add 600 mL of glacial
acetic acid, 260 mL of methanol, 140 mL of 119
g/L potassium bromide solution to a 1 L volumetric
flask. Bring to volume to deionized or distilled
water. Transfer the solution to a reagent bottle.
DEVICE PREPARATION
• Connect the reagent bottle top assembly to the bottle
of prepared reagent.
• Assemble the titration vessel according to the
instruction manual.
3-6
HI9901EN BROMINE INDEX OF AROMATIC HYDROCARBONS
Adaptation of ASTM D1492-08
mg (Br)/100g.
from the main screen. Use the arrow
• Press
keys to highlight HI9901EN BrIndex of Aromatics
and press .
• Dispense enough reagent from the reagent bottle to
fill the vessel to the "min" line (about 100 mL).
• Press key to pre-titrate the solvent and the
titration vessel moisture. Allow the background drift
rate to stabilize before proceeding to the next step.
ANALYSIS
• Fill and weigh the syringe and needle with the
sample.
• Press . You will be prompted to enter the
sample size.
• Enter the Estimated Bromine Index. The titrator will
recommend the optimal sample size to be added to
the titration vessel. Dispense the amount provided
from the optimal sample size into the titration vessel
through the septum using the needle. Pay attention
not to get any sample on the electrode or vessel walls.
If necessary swirl the titration vessel by and to remove
any standard on the electrode or beaker wall.
• Clear the needle of residual sample by in taking
a small volume of air from the titration vessel. If a
"hanging drop" of sample is seen on the end of the
needle, dip the end of the needle briefly in the solvent.
• Remove the needle from the titration vessel and
weigh the syringe again in order to determine
the added sample mass (by difference of the two
measurements.)
• Use the numeric keypad to enter the exact weight
and press key to start the analysis.
• At the end of the titration, the Sample Analysis
Result screen is displayed. The results are expressed
in mg (Br)/100g.