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pH result of water not within specified standard


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#1 carine

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Posted 27 December 2018 - 01:54 AM

Hi all, 

 

Our product is edible ice, and our raw material purely potable water, we found pH reading lower than the required standard (6.5 to 8.5).. Anyone have experienced this before and what are the corrective action can be done? Thanks in advance. 



#2 beautiophile

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Posted 27 December 2018 - 03:42 AM

What is the temperature while water's pH is measured?

Mostly, pH meters measure the resistance (conductivity) related to H3O+ in the water. In standard condition (1 atm, 20 degree Celcius), the pH of pure water is 7 since the hydrolysis constant of water is 10^(-14). When the water gets hotter, it is hydrolysed more then the hydrolysis constant increases because more H3O+ and OH- are released; for instance 10^(-12), a.k.a. the pH becomes 6. In the other words, the pH of neutral water depends on its temperature.



#3 carine

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Posted 27 December 2018 - 07:29 AM

Dear Beautiophile, 

 

Im not so sure how the pH being measured as we sent out d sample to outsource lab. 

 

Based on your statement, the hotter the temperature of water , the lower the pH will be due to more Hydrogen than Hydroxyl Ion released. Hence, may i kmow what is the standard temperature for pH measuring?  



#4 beautiophile

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Posted 28 December 2018 - 02:26 AM

Hi Carine,

There are no standard temperatures for pH measurement.

I can see that your purpose is to ensure the neutrality of your water, neither sour nor basic. Since you outsource a professional lab, you can ask them for water-neutrality test reports including:

- Temperature of the water sample.

- Recorded pH of the water sample.

- Neutral pH of water at the above temperature (e.g. from chemistry handbooks) or the measured pH of the lab's reference pure water in the same measuring condition.

- Definition of the acceptable range = "neutral/reference pH" +/- 1.0, (or 0.5 or 1.5, based on your own requirements) 

- Conclusion of the (non)conformity of tested water sample against the acceptance pH range.

Regards.



#5 Charles.C

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Posted 29 December 2018 - 11:49 AM

Dear Beautiophile, 

 

Im not so sure how the pH being measured as we sent out d sample to outsource lab. 

 

Based on your statement, the hotter the temperature of water , the lower the pH will be due to more Hydrogen than Hydroxyl Ion released. Hence, may i kmow what is the standard temperature for pH measuring?  

 

Hi carine,

 

Solution Temperature Compensation (STC) (whether this is needed will depend on the pH accuracy required) converts the pH at the measurement temperature to the pH at a reference temperature.

The reference temperature is generally 25°C. Only pH values taken at the same temperature or converted using solution temperature compensation can be compared to each other

https://www.westlab....ature-affect-ph

 

These articles may also be of casual  interest -

 

https://www.westlab....ature-affect-ph

https://webcache.goo...n&ct=clnk&gl=th

 

So what were the reported lab results ?

 

Is this Metropolitan water ?

 

Or just one isolated lot/potential well water supplier/?? ?


Kind Regards,

 

Charles.C


#6 kkaiser

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Posted 03 January 2019 - 08:02 PM

Temperature will affect the pH reading for sure! Some meters use temp compensation.. and if you're sending it to a lab, I'd bet they're accounting for that. The pH should read correctly to 32 degrees F.. as the temp lowers the pH will also lower. 






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