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Author: Subject: ph paper seems off
itsafineday
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[*] posted on 16-10-2019 at 07:50
ph paper seems off


I have calibrated two cheap ph meters using calibration solutions mixed with distilled (and ozonated) water.

I also have a book of universal indicator ph strips.

When I measure a fertilizer solution with the paper it indicates a ph of 7 . When I use the two calibrated meters I get a ph of 5.3.

The fertilizer solution does have some color but I do not feel as though it is obscuring the ph papers reaction.

I am not sure why this is and hope someone here might be able to help explain this .

Sorry if this is spoon feeding . Thanks.




I am seeking to level up my Chem skills. Corrections welcome! All mentorship in madness appreciated.
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SWIM
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[*] posted on 16-10-2019 at 09:44


How about trying both the strips and meters on distilled water and a few standard strength solutions you make up?

See if they test differently in several situations.

Have you got a good scale and volumetric flask?

Are the strips for lab use or are they the ones they sell for spas and fishponds and such?
Are they less than a few years old?
(Just trying to eliminate a few possibilities here: Could it be the strips?)

Since you've got 2 meters which read the same and it's way off from the indicator strips I'm betting the strips are the problem.

I use universal ph paper regularly, but I've never really tried to determine how accurate it is.
It sure ought to be better than that, I'd hope.

Do you have any regular litmus paper? If so try some of that. If the litmus says acid like the meters and the universal still says neutral I'd really wonder about that paper.

EDIT: as for spoon feeding. This clearly isn't that. You've got a procedural problem in something you're doing and it's not the kind of think you can easily look up in a book.
However It's EXACTLY the kind of thing some posters with personal experience should be able to help you with.

This is pretty much why this place is here.


[Edited on 16-10-2019 by SWIM]




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itsafineday
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[*] posted on 16-10-2019 at 12:08


Thanks SWIM. The ph paper is "Lab Supplies" Brand . It says its Litmus ph strips. I checked against my calibraton solutions and some distilled water (I used a 250ml graduated cylinder to measure the water). It seems to be pointing to an error in the printed ph scale of the strips. Again, thank you.



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Deathunter88
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[*] posted on 17-10-2019 at 07:03


Quote: Originally posted by itsafineday  
I have calibrated two cheap ph meters using calibration solutions mixed with distilled (and ozonated) water.

I also have a book of universal indicator ph strips.

When I measure a fertilizer solution with the paper it indicates a ph of 7 . When I use the two calibrated meters I get a ph of 5.3.

The fertilizer solution does have some color but I do not feel as though it is obscuring the ph papers reaction.

I am not sure why this is and hope someone here might be able to help explain this .

Sorry if this is spoon feeding . Thanks.


Helps to look stuff up sometimes. Heres a link to the amazon page for your pH paper. https://www.amazon.com/Litmus-Strips-Universal-Application-P...

Read the one star reviews.

[Edited on 17-10-2019 by Deathunter88]
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SWIM
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[*] posted on 17-10-2019 at 10:29


Quote: Originally posted by Deathunter88  
Quote: Originally posted by itsafineday  
I have calibrated two cheap ph meters using calibration solutions mixed with distilled (and ozonated) water.

I also have a book of universal indicator ph strips.

When I measure a fertilizer solution with the paper it indicates a ph of 7 . When I use the two calibrated meters I get a ph of 5.3.

The fertilizer solution does have some color but I do not feel as though it is obscuring the ph papers reaction.

I am not sure why this is and hope someone here might be able to help explain this .

Sorry if this is spoon feeding . Thanks.


Helps to look stuff up sometimes. Heres a link to the amazon page for your pH paper. https://www.amazon.com/Litmus-Strips-Universal-Application-P...

Read the one star reviews.

[Edited on 17-10-2019 by Deathunter88]


Now here's a poster who knows what the right first question to ask is.
Wish I'd thought to do that.

I've had good results with Hydrion brand indicator strips.
I used their broad ph range paper and Haven't had any problems, but I haven't tested it against calibrated equipment.

It is pretty popular though, and has been around a long time so they probably have pretty good quality control standards.




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G-Coupled
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[*] posted on 17-10-2019 at 13:09


Moral of the story: Don't trust Chinesium pH papers with low review scores?
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draculic acid69
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[*] posted on 17-10-2019 at 18:53


Hah, chinesium.funny.
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itsafineday
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[*] posted on 18-10-2019 at 11:00


Quote: Originally posted by G-Coupled  
Moral of the story: Don't trust Chinesium pH papers with low review scores?


I got these as a gift from someone who isn't into chemistry. Unfortunately most review systems are gamed these days and trusting review reviewers is also not a good idea. Most of the chinese garbage is coming through american front companies bought up by china.

I've been fighting for a refund from the now chinese company General Electric for months now. They just refused to pick up the paperwork they required for the mail in refund (after I bought another air conditioner per their instructions to get the refund). I was smart enough to send it back with tracking but I guess that doesn't matter either.

china sucks.

The one star reviews do tell the tale , though.

Trust is dead.

[Edited on 18-10-2019 by itsafineday]

[Edited on 18-10-2019 by itsafineday]

[Edited on 18-10-2019 by itsafineday]




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[*] posted on 18-10-2019 at 12:46


That sucks - don't get me wrong, the Chinese are capable of making some fantastic stuff, but a lot of Chinese vendors seem content to sell out of date, or sub par stuff without telling the buyers.

Caveat Emptor, and all that.




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