Total Alkalinity, NaOH/KOH, And Percent Spent

Question 1

2. Preparing samples

Answer 1

•place 200mL volumetric flask on balance and tare
•Pipette 7mL of sample into flask and record weight on daily worksheet (in case of weak caustics the sample will be analyzed by directly pipetting 5mL of sample into 300 mL beaker with DI water (ex: 16 vent gas water and 01 coalescer))
•fill volumetric flask containing sample up to line (200mL mark) with DI water, mix well
•fill 300mL plastic beaker with ~145mL DI water
Transfer 5mL diluted caustic into 300mL beaker of DI water
•follow steps 1-5 until all samples prepared
•load 300mL beakers into numbered positions on sample carousel. Place beakers in order listed in Tiamo software sample table or edit sample table as necessary
•assemble Titrate with 0.1N Hydrochloric acid exchange unit locked into 904 Titrando and proper pH probe (6.0210.100) in place. When probe not jn use it should be stored in 3M KCl solution

Question 2

3. Programming the instrument

Answer 2

•load Tiamo software and click workplace then determination series
Click sample table and load the appropriate sample table
•double click each sample and enter weight recorded for each sample
•click apply to save changes
•click manual icon and dose the Titrant to make sure no air bubbles present
•once all info is stored, click start

Question 3

4. Data analysis

Answer 3

• click database then select reprocess on desired sample
• if there are three or more endpoints, use curve evaluation tab to manipulate graph down to 2 endpoints. Curve evaluation tab is important and is only place that shows the derivative of the curve-if the curve needs to be modified click Edit button
• make sure endpoints line up with peaks in curve. Add, delete or move endpoints as needed
• pH of sample at desired endpoints will be from 9-6 for first endpoint and from 6-3 for second endpoint
• to delete endpoints, select hand tool;to add endpoints, click cross hairs tool
• once editing finished click OK and YES when it asks you if you want to modify. After this select recalculate to have changes take place

Question 4

5. Interpretation of Results

Answer 4

•Strong base:
••when only one break in titration curve is present in pH range from 9 to 6, this break will be considered endpoint of all strong bases present
••when two breaks in titration curve present, first break will be considered endpoint in all strong bases present
••when three breaks in titration curve present, second break will be considered end point of all strong bases present
•weak base:
••when two breaks present, second break considered endpoint of all weak bases present
••when three breaks present, third break in curve will be considered weak base endpoint
•Total Alkalinity: Sum of Strong Base and Weak Base
••when two breaks present, second break will be considered endpoint for all bases present
••when three breaks present, third break will be considered endpoint of all bases present
%spent: Difference between Strong Base and Total Alkalinity expressed as percent

• *for weak bases sub as 16 vent gas water, since the dilution factor is not used, the strong base and or total alkalinity need to be divided by 40. If only one endpoint exists, report the %spent as 0. If two endpoints exist, report spent as is. If graph starts in weak base range, and there is only one endpoint, report %spent as 100.
• *for strong bases, if only one endpoint the value will be reported for both NaOH/KOH and total alkalinity. In this case, spent reported as zero.

Question 5

6. QC standards

Answer 5

• approximately 5mL of 1N sodium hydroxide solution is prepared the same as samples
• normally there will be a 200mL volumetric prepared and labeled NaOH Std along with weight of 1N Sodium Hydroxide solution
• standard run daily before routine samples and results recorded in NWA

Question 6

7. Troubleshoot

Answer 6

Probe
•check that correct probe used
•run pH cal if operation of probe is jn question. Slope should be between 95-105. 4 pH buffer should have reading of -150 to -200mV. If you are not seeing this it may be that buffers need replaced and cups need wiped out
•clean fruit on probe with fresh emery paper and toluene
•ensure probe is stored jn fresh 3M KCl(if it’s not pink or too pink, needs refreshed)
Titrant
•check that 0.1N Hydrochloric acid exchange unit is connected to 904 titrino
•visually confirm there are no air bubbles in Titrant buret. If air bubbles dose at least 2 times

Question 7

1. Purpose

Answer 7

Determine concentration of strong base, weak base, and total alkalinity in fresh and used refinery caustics. Determination ensures the concentration of caustic is correct for neutralization/extraction process to be performed by caustic