pH Electrode Calibration Procedure
All pH electrodes require calibration from time to time. A two point calibration characterizes an electrode with a specific pH meter. Once an electrode is characterized, the electrode/meter pair can be used to determine the pH of a solution. Please follow the step-by-step procedure outlined below to perform a two point calibration. A 7.00 pH buffer solution and a 4.01 pH buffer solution are required.
1) Rinse the electrode thoroughly with D.I. water to remove all traces of storage solution, process medium, or previous test solution. Thoroughly rinse the electrode after each buffer test to prevent carry over contamination of the pH buffer solutions. Gently blot the electrode on a soft tissue to remove the excess rinse water. Do not rub the bulb since it can cause a static charge build-up.
2) Insert the electrode and the A.T.C. (automatic temperature compensator) in 7.00 pH buffer solution. Allow 30 seconds for the electrode/A.T.C. to reach thermal equilibrium with the buffer solution. Adjust the pH meter with the standardize/zero control for a pH indication equal to 7.00.
Note: If the meter does not have an A.T.C., place a thermometer along with the electrode in the 7.00 pH buffer solution. Allow 30 seconds for the pair to reach thermal equilibrium with the buffer. Adjust the temperature dial on the meter to correspond with the thermometer reading. Then adjust the pH meter with the standardize/zero control for a pH indication equal to 7.00.
3) Repeat Step 1, and insert the electrode and the A.T.C. in a 4.01 buffer solution. Allow 30 seconds before adjusting the pH meter with the slope/span control for a pH indication equal to 4.01.
4) Repeat Steps 2 and 3 to maximize the precision of the calibration.
Notes:
a) Always use fresh pH buffer solutions for the most accurate results.
b) A 10.00 pH buffer solution may be substituted for the 4.01 pH buffer solution in Step 3. All pH buffer solutions above 7.00 pH are less
stable and have a limited life. These high pH buffers will more readily absorb CO2 from the atmosphere and will typically change to a lower pH value when left open. For this reason, a 4.01 buffer solution is recommended to perform a reliable two point calibration. Also, the buffers should bracket the desired pH range.
c) When a pH electrode is calibrated with an autocalibration meter, consult the meter’s operation manual for the required calibration procedure.
pH Electrode Storage Procedure
When a pH electrode is not in use, the bulb should be kept in a wetted environment. Dehydration of the bulb will temporarily impair the electrode’s performance. The following storage procedure is recommended when the electrode is not in use.
1) Short-Term: Immerse the electrode in 3.8M KCI solution (Broadley-James Part Number: AS-3120-C20-0500). Do not store electrode in D.I. water.
2) Long-Term: Fill soaker bottle (Broadley-James Part Number: AM-1050-12) with fresh 3.8M KCI solution and insert electrode. The soaker bottle O-ring should be securely in place, and the cap should be hand tightened. Do not store electrode in D.I. water.
pH Electrode Test Procedure
The purpose of this test is to determine if a pH electrode is functioning within acceptable limits. The A. P. (asymmetry potential) and slope (efficiency) can be used as guidelines to judge an electrode’s performance. Typically an electrode is replaced when the
A. P. is greater than ±20 mV and/or the slope drops below 91%. Consideration should also be given to the electrode’s speed of response. Please follow this step-by-step procedure to determine the performance of an electrode. Required test equipment includes 7.00 and 4.01 pH buffer solutions with a pH meter that has an mV readout.
1) Set the pH/mV switch on the pH meter to the mV position.
2) Connect a shorting plug to the input on the pH meter, or connect a precision mV generator with a 0 mV input. Adust the standardize/zero
control on the pH meter for a reading equal to 0.0 mV.
3) Disconnect the shorting plug/precision mV generator, and connect the electrode that will be tested.
4) Rinse the electrode thoroughly with D.I. water to remove all traces of storage solution, process medium, or previous test solution. Thoroughly rinse the electrode after each buffer test to prevent carry over contamination of the pH buffer solutions. Gently blot the electrode on a soft tissue to remove the excess rinse water. Do not rub the bulb since it can cause a static charge build-up.
5) Insert the electrode and the A.T.C. (automatic temperature compensator) in 7.00 pH buffer solution. Allow 30 seconds for the electrode/A.TC. to reach thermal equilibrium with the buffer solution. Record the polarity and the mV reading. This is the asymmetry potential of the electrode. Ideally the electrode should have an A. P. equal to 0 mV.
Note: If the meter does not have an A.T.C., place a thermometer along with the electrode in the 7.00 pH buffer solution. Allow 30 seconds for the pair to reach thermal equilibrium with the buffer. Adust the temperature dial on the meter to correspond with the thermometer reading. Record the polarity and the mV reading to determine the A. P.
6) Repeat Step 4, and insert the electrode and the A.T.C. in a 4.01 buffer solution. Allow 30 seconds before recording the mV reading.
7) Determine the mathematical difference between the two mV readings. This is the electrode’s span.
8) Divide the electrode’s span by the theoretical span of 176.9 mV (at 25ºC) and multiply by 100. This determines the slope of the electrode.
Note: For best results, the pH buffer solutions should be used at 25ºC. Otherwise, record the temperature of the buffer and determine the temperature adjusted pH with the temperature coefficient charts printed on the buffer container.
Monday, April 27, 2009
Friday, February 27, 2009
Safety Slogans
A Collection of Safety Slogans:
Success is no accident
Never forget about safety
BEST BE Safe Today
Stand up for safety
Work safely to-day and every day
Speak up for safety
Be aware Take care
Zero compromise towards safety
Safety is no accident
Always think safety no matter what the task
Always look after No.1 and if you need help just ask
Think safety avoid unsafe acts
Play it safe
Know safety No Accidents
The first 3 letters in workplace safety YOU
More waste prevention + more recycling =Less waste = Less landfill
Even in a hi-tech world you eyes are still your greatest asset
Check for safety then recheck
Put your brakes on speed
Think safety - it couldn't hurt
Every accident - every - time if it's predictable it's preventable
Have you an eye for safety or are you blinded by bad habits
Never give safety a day off
Let safety be a sponge - soak it up
Safety is a way of life
Risk - is is worth it?
Safety begins with No. 1
Your good health is your greatest wealth
Stop unsafe acts now
Be sure be safe
Safety first and last longer
Safety - it's in your hands
Be aware - Take care
Safety is free use it generously
Safety is our business too
Accident prevention - Your No. 1 intention
Hear to-day gone tomorrow - use you hearing protection
Think positive an accident is only an attitude away
Safety is success by purpose - Not Accident
Safety records don't happen by accident
If you are aware of it take care of it
Safety is the most productive business
Safety begins with teamwork
Watch your step - it could be your last
Zero tolerance on safety
Safety awareness saves lives
Safety - a good friend to take home
Better to lock out than luck out
Make safety a reality and don't be a fatality
When walkways freeze - walk safely please
Safety First, Last and Always
The goal must be zero accidents
You will achieve the level of safety excellence that you demonstrate you want
Failing to prepare = Prepare to fail
Safe to do? Ask
Work smarter not harder
Don't get caught in the web of unsafe acts
Wipe up and avoid a slip up
We need you - work safely
Working without safety is a dead end job
Don't get caught with your guard off - it could be disarming
Guard against man eating machines
Safety is our goal what's yours?
Do the do's not the don't s
To avoid a scene keep your workplace clean
Stop! Think! Then Act!
A harness is better than a hearse
Be aware of slips and trips
Zero in on safety
Team up to safety
Safety starts with S but begins with you
The door to safety swings on the hinges of common sense
Safety is a state of mind - Accidents are an abscence of mind
A wound neglected is a wound infected
Normal speed meets every need
Stop accidents before they stop you
Look sharp don't get cut
Before you start be safety smart
Safety is a full time job - don't make it a part time practice
10 fingers. 10 toes, If you are not safe Who knows?
You get what you inspect, not what you expect
Work safely or Hurt greatly
Safety comes before schedule only in the dictionary
The safety risk is the one you didn't take
KISS Keep it Safe and Sound
A casual attitude towards safety = CASUALTY
Safety is as simple as ABC - Always Be Careful
You safety gears are between your ears
Make your plant the best - safer than all the rest
Know safety - No injury, No safety - Know injury
Get the safety habit
Don't fix the blame, fix the problem
Hearing protection is a sound investment
One safe act can lead to another
Tell me- I forget, Show me - I remember, Involve me - I'committed
Communication
Urge
Leadership
Teamwork
Understanding
Recognition
Empowerment
Shortcuts cut life short
No Safety - Know Pain, Know Safety - No Pain
It's better to correct an unsafe friend than to bury one
You can eat with false teeth, you can't see with a glass eye
Be a safety hero - score an accident zero
Safety - it's the tool for LIFE
Safety comes in a can, I can, You can, We can be safe
When you gamblw with safety you bet your life
Safety has no time out
New Year Resolution - if its unsafe I will find a solution
Safety - Live with it
Safety - everyone's full time job
When in doubt get out
Safety in - we win
The chance taker is the accident maker
Lifting's a breeze when you bend at the knees
Safety Glasses - All in favor say EYE
Success is no accident
Never forget about safety
BEST BE Safe Today
Stand up for safety
Work safely to-day and every day
Speak up for safety
Be aware Take care
Zero compromise towards safety
Safety is no accident
Always think safety no matter what the task
Always look after No.1 and if you need help just ask
Think safety avoid unsafe acts
Play it safe
Know safety No Accidents
The first 3 letters in workplace safety YOU
More waste prevention + more recycling =Less waste = Less landfill
Even in a hi-tech world you eyes are still your greatest asset
Check for safety then recheck
Put your brakes on speed
Think safety - it couldn't hurt
Every accident - every - time if it's predictable it's preventable
Have you an eye for safety or are you blinded by bad habits
Never give safety a day off
Let safety be a sponge - soak it up
Safety is a way of life
Risk - is is worth it?
Safety begins with No. 1
Your good health is your greatest wealth
Stop unsafe acts now
Be sure be safe
Safety first and last longer
Safety - it's in your hands
Be aware - Take care
Safety is free use it generously
Safety is our business too
Accident prevention - Your No. 1 intention
Hear to-day gone tomorrow - use you hearing protection
Think positive an accident is only an attitude away
Safety is success by purpose - Not Accident
Safety records don't happen by accident
If you are aware of it take care of it
Safety is the most productive business
Safety begins with teamwork
Watch your step - it could be your last
Zero tolerance on safety
Safety awareness saves lives
Safety - a good friend to take home
Better to lock out than luck out
Make safety a reality and don't be a fatality
When walkways freeze - walk safely please
Safety First, Last and Always
The goal must be zero accidents
You will achieve the level of safety excellence that you demonstrate you want
Failing to prepare = Prepare to fail
Safe to do? Ask
Work smarter not harder
Don't get caught in the web of unsafe acts
Wipe up and avoid a slip up
We need you - work safely
Working without safety is a dead end job
Don't get caught with your guard off - it could be disarming
Guard against man eating machines
Safety is our goal what's yours?
Do the do's not the don't s
To avoid a scene keep your workplace clean
Stop! Think! Then Act!
A harness is better than a hearse
Be aware of slips and trips
Zero in on safety
Team up to safety
Safety starts with S but begins with you
The door to safety swings on the hinges of common sense
Safety is a state of mind - Accidents are an abscence of mind
A wound neglected is a wound infected
Normal speed meets every need
Stop accidents before they stop you
Look sharp don't get cut
Before you start be safety smart
Safety is a full time job - don't make it a part time practice
10 fingers. 10 toes, If you are not safe Who knows?
You get what you inspect, not what you expect
Work safely or Hurt greatly
Safety comes before schedule only in the dictionary
The safety risk is the one you didn't take
KISS Keep it Safe and Sound
A casual attitude towards safety = CASUALTY
Safety is as simple as ABC - Always Be Careful
You safety gears are between your ears
Make your plant the best - safer than all the rest
Know safety - No injury, No safety - Know injury
Get the safety habit
Don't fix the blame, fix the problem
Hearing protection is a sound investment
One safe act can lead to another
Tell me- I forget, Show me - I remember, Involve me - I'committed
Communication
Urge
Leadership
Teamwork
Understanding
Recognition
Empowerment
Shortcuts cut life short
No Safety - Know Pain, Know Safety - No Pain
It's better to correct an unsafe friend than to bury one
You can eat with false teeth, you can't see with a glass eye
Be a safety hero - score an accident zero
Safety - it's the tool for LIFE
Safety comes in a can, I can, You can, We can be safe
When you gamblw with safety you bet your life
Safety has no time out
New Year Resolution - if its unsafe I will find a solution
Safety - Live with it
Safety - everyone's full time job
When in doubt get out
Safety in - we win
The chance taker is the accident maker
Lifting's a breeze when you bend at the knees
Safety Glasses - All in favor say EYE
Thursday, February 19, 2009
Gas Flow Calculation
Gas Flow Calculation
Flowmeters are calibrated for a specific gas (e.g. nitrogen for the RTA). To calculate the flow rate of another gas, multiply the reading by the ratio of the conversion factor or the desired gas to the conversion factor for the calibration gas. For example on the RTA (calibrated for nitrogen), if the indication is 200 ml/min and the gas is Argon, the actual flow rate is 200 * 1.443=288 ml/min.
GAS FACTOR
Nitrogen 1.00
Oxygen .996
Argon 1.443
Air 1.00
Helium 1.454
Water Vapor 0.817
Flowmeters are calibrated for a specific gas (e.g. nitrogen for the RTA). To calculate the flow rate of another gas, multiply the reading by the ratio of the conversion factor or the desired gas to the conversion factor for the calibration gas. For example on the RTA (calibrated for nitrogen), if the indication is 200 ml/min and the gas is Argon, the actual flow rate is 200 * 1.443=288 ml/min.
GAS FACTOR
Nitrogen 1.00
Oxygen .996
Argon 1.443
Air 1.00
Helium 1.454
Water Vapor 0.817
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