Hanna Instruments HI 904 - Manual (Page 89)

6-7
TITRATION
Manual Entry
Follow the steps below:
1. Attach a long needle (approximately 6 in. for best control) to a syringe that is large
enough to hold at least one complete sample volume. For the volumetric addition of
samples, use a precision-volume syringe.
2. Rinse the syringe and needle with sample 2-3 times by drawing in a small portion of
sample, fully extending the plunger, shaking to coat the syringe interior, and expelling
the sample into a waste collection container.
3. For samples with low water content (less than 200 ppm), the final syringe rinse should
not include drawing in air – humidity in the air could significantly contaminate the sample.
4. Draw enough sample into the syringe for at least one titration.
5. Dry the outside of the needle with a lint-free wipe or tissue.
6. For samples by mass, place the full syringe with needle on an analytical balance. Tare the
balance (back-weighing technique).
7. Insert the needle through the septum in the sample port. Push the syringe through the
septum until the end of the needle is approximately 1 cm from the surface of the reagent.
8. Steadily dispense the appropriate amount of sample, ensuring that the sample is introduced
directly into the reagent and does not splash or spatter onto the wall of the titration
vessel or electrodes.
9. For samples by mass, draw a small amount of air from inside the titration vessel into the
syringe to ensure that no sample drops remain on the tip of the needle.
10. If a drop is observed on the needle, briefly dip the needle into the reagent to remove it.
11. Remove the syringe and needle from the septum taking care to not touch the needle to
the other internal vessel components.
12. Enter the dispensed amount of sample. For samples by mass, re-weigh the syringe to
determine the mass of dispensed sample (back-weighing technique).