Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: sk36 on March 29, 2015, 02:30:26 PM
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As of now, I'm a Trainee Chemist in textile testing. I just readed the SOP of checking pH in textiles and know the process, but i didn't know why pH is needed in textiles and what's happening in the process. I came to know that pH should be checked in textiles and if it isn't in a limit, it may cause skin irritation. But is that a only reason for testing? I want to explore more, hope some experts here can able to help me.
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Another reason to test pH is to verify a process. If an extreme pH is used to say, dye a fabric, or even generate synthetic fibers, then you'll want to check a pH to be certain a process is done. Obviously, if no one ever forgets a step, and the process always works, such testing would be unnecessary. But process checks exist in numerous products, from housing materials, to textiles to the most obvious, pharmaceuticals and foods.
I do you your methods are good and you understand them well. Taking the pH of a dry solid is pretty much impossible, and even a moistened solid is a little dubious. I don't know if that's what's confusing you.
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I do you your methods are good and you understand them well. Taking the pH of a dry solid is pretty much impossible, and even a moistened solid is a little dubious. I don't know if that's what's confusing you.
It's not taking pH of a solid fabric directly, the process is we have to cut them, and dipped in 0.1M KCL solution in a rotational shaker for hours, and then the solution's pH is noted. I don't know what is the reaction happening here. Also inhave one more question, i checked pH of distilled water in our lab and it is 6.0, at 23 degree. I boiled the water for around 20 minutes and then allowing it to cool to attain the same temperature (23 degree), now the pH of the water is almost 6.8, i don't know what cause such an increase in pH, I'm sure no other things contaminated.
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It's not taking pH of a solid fabric directly, the process is we have to cut them, and dipped in 0.1M KCL solution in a rotational shaker for hours, and then the solution's pH is noted. I don't know what is the reaction happening here.
Simple dissolution and dissociation. If there are any acids/acidic groups on the surface (or close to the surface) they will release the protons, acidifying the solution.
While this is not necessarily measuring "pH of the solid", as long as you are accurately repeating the procedure you can compare amount of acids in samples - those with more acid present will produce solution with lower pH.
Also inhave one more question, i checked pH of distilled water in our lab and it is 6.0, at 23 degree. I boiled the water for around 20 minutes and then allowing it to cool to attain the same temperature (23 degree), now the pH of the water is almost 6.8, i don't know what cause such an increase in pH, I'm sure no other things contaminated.
Think atmospheric CO2.
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Think atmospheric CO2.
Yeah.. But still i wonder because, im closing the beaker with a petri dish, even though the pH is reaching 7.
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Fibre strength? Dye fading? Dye fastness?
I'm speculating about which fabric attributes might be affected by pH.
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Yeah.. But still i wonder because, im closing the beaker with a petri dish, even though the pH is reaching 7.
The evolved CO2 may not re-dissolve very easily.
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It's not taking pH of a solid fabric directly, the process is we have to cut them, and dipped in 0.1M KCL solution in a rotational shaker for hours, and then the solution's pH is noted. I don't know what is the reaction happening here.
Simple dissolution and dissociation. If there are any acids/acidic groups on the surface (or close to the surface) they will release the protons, acidifying the solution.
While this is not necessarily measuring "pH of the solid", as long as you are accurately repeating the procedure you can compare amount of acids in samples - those with more acid present will produce solution with lower pH.
Also inhave one more question, i checked pH of distilled water in our lab and it is 6.0, at 23 degree. I boiled the water for around 20 minutes and then allowing it to cool to attain the same temperature (23 degree), now the pH of the water is almost 6.8, i don't know what cause such an increase in pH, I'm sure no other things contaminated.
Think atmospheric CO2.
We did a comparison in our lab of tap water, distilled water and the MilliQ (reverse osmosis- deionized) water since the tap water & MilliQ water were close to pH 7 while the distilled water always had a lower pH at like 5.8. We sent it out to have ICP-MS done on all three. The MilliQ not surprisingly was the most pure, but the startling thing about the distilled water was that it was much higher in boron than the other two. Perhaps boron, being a very small molecule, is preferentially evaporated with the water and concentrated in the distilled water as boric acid, thus lowering the pH. You boiling it with an open system might then remove this boron. (just hypothesizing).
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Another reason to test pH is to verify a process. If an extreme pH is used to say, dye a fabric, or even generate synthetic fibers, then you'll want to check a pH to be certain a process is done. Obviously, if no one ever forgets a step, and the process always works, such testing would be unnecessary. But process checks exist in numerous products, from housing materials, to textiles to the most obvious, pharmaceuticals and foods.
I do you your methods are good and you understand them well. Taking the pH of a dry solid is pretty much impossible, and even a moistened solid is a little dubious. I don't know if that's what's confusing you.
Typically KCl, K2SO4 or NaCl solutions are used with textiles to increase dye permeability of the fibres
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the startling thing about the distilled water was that it was much higher in boron than the other two. Perhaps boron, being a very small molecule, is preferentially evaporated with the water
Somehow I doubt boron volatility, but I wouldn't be surprised if the boron was washed out from cooler and whatever vessel it is collected in.
Many years ago we made our own triple distilled water for electrochemistry, using some standard lab distiller as a first step, and combined two step fused quartz distiller - no boron possible.
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What sort of setup did you use to make the distilled water? Glass?
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the startling thing about the distilled water was that it was much higher in boron than the other two. Perhaps boron, being a very small molecule, is preferentially evaporated with the water
Somehow I doubt boron volatility, but I wouldn't be surprised if the boron was washed out from cooler and whatever vessel it is collected in.
Many years ago we made our own triple distilled water for electrochemistry, using some standard lab distiller as a first step, and combined two step fused quartz distiller - no boron possible.
Yeah, it made no sense to me either since boric acid has a boiling point of 300 C. But attached below is the ICP-MS report of the three water samples -- A is the MilliQ Deionized water, B was the tap water and C was the distilled water. The only major difference with the distilled water that I thought could possibly account for the decreased pH was the much higher boron than the other two samples (still only 551 ug/L). Could it be possible the boron was dissolved as more volatile boron halide species? (Samples B & C were diluted 1:1 while A was undiluted hence the difference in RDLs)
@curiouscat -- we use a Water Precision Systems Distiller model PWS 12-12
http://www.precisioncanada.com/water/pws1212.html
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi60.tinypic.com%2Fatoe9g.jpg&hash=14127b53bb21a2adfc6266f1da4b3f3cb2416ee5)
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Would the boron explain a ph of 5.8 anyways? These are very low ppm / ppb values right? Would the [H+] be large enough to explain 5.8?
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Would the boron explain a ph of 5.8 anyways? These are very low ppm / ppb values right? Would the [H+] be large enough to explain 5.8?
Yeah not sure. Just we were always getting lower pH from distilled water than the tap water & MilliQ water. We even went and bought commercial distilled water and it had lower pH around pH 6. I guess it will remain a mystery.
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Very little CO2 ought to be enough to bring pH down to those levels. So the 5.8 pH of your distilled water by itself doesn't strike me as odd.
Now take tap water. Although that too must have CO2 dissolved with all those relatively massive quantities of others ions (compared to distilled / RO) could conceivably have some sort of buffering effect. That compensates the acidity of CO2 & keeps pH at 7. Does that make sense?
Then, the real surprise is the RO water. Why isn't that 5.8 too. Now that I don't know. Must think.
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Sometimes it's easy to overlook obvious things. I'm not saying this is the case, but is the pH meter you are using properly calibrated?
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Yes, the QA/QC technician calibrates them every morning, and I tested the waters using three different pH electrodes with all similar results. However, titratable acidity was also performed on the distilled water and it was virtually zero (meaning the smallest drop of 0.1 N NaOH raises pH to over 10 and titration stops).
Also, distilled water having a low pH is not uncommon. If you look on internet, you will see many websites asking about this (mostly people with aquariums asking if it is ok for fish with lower pH). Most give the reason Curiouscat does being dissolved CO2 (as carbonic acid). I just found it very strange the boron was 14 times higher in the distilled water than the tap water, yet the same tap water supplies that distiller unit.