ph_measurement

[emkee]

callin out for some help. i m testing ph of a fluid. the strips used are salmon orange.
with a indicator range from 1->red till 14->brown.
i need the ph to b around 7.6->yellow(7) green( 8) .
the problem is the strip colors different on different places of the strip. so there is no way for me to know for sure. example dip it in, the beginning turns brown the middle kind of orange and the end part green. the explanation that accompanied the strips says to compare within 30 seconds.
how do this things work. which spot is the right place to measure ph.
thanks for any help or links.

 

[Deus121]

The paper itself (Litmus paper) reacts in the solution. The color can be kinda multi-colored at the solution-line (where air meets solution), I'd use the end, the part that was completly submurged in the solution. If the paper thats submurged in the solution itself is turning different colors at different levels, then prehaps you have different layers that are different phs.

 

[emkee]

wow thats fast deus. thanks i will look at the part that was in the fluid. the color changes on the paper were appearing when the fluid was sucked into the paper. the part that was in the solution remained a constant color which i will use for measurement.

 

[emkee]

i finished the product ph is around 7.5. so that worked well. very thankful for the assistance with measuring.
now there one thing i liked to get confirmed because there is a tiny bit of white residue on the bottom of my pirex dish.
could it be possible there is any unreacted NaOH
in there. in possible case of ingestion could this hurt. as the PH is right and the final product smells lactone.

 

[PhreeX]

If the pH is right, you know it's not going to burn a hole through your throat, so take a cap and see how it is... not 100% sure what the white residue is...