The manual doesn't really say what can be connected. It just says "Recorder Output 1400mV". When I connect a vom to the + and - recorder terminals it reads for example 700 mV when the pH meter dispays a pH of 7.0.
When I connect the pH meter terminals to the circuit the vom reads an amplified voltage but the pH meter pops and reads 1, which looks like an error code. The manual does not have any codes nor schematics and I have searched and couldn't find any.
I did use a 100k pot instead of the 24.9 k resistor in your schematic and set that at 24.9k before installing.

 

See "Op Amps for Everyone"; its free on the TI site. Chapter 4 shows how to use simultaneous equations to obtain the resistor values. Op amp selection and pot size is determined by the methods shown here. Gain and offset adjustments react in a single op amp circuit, so you might want to cascade op amps to minimize the effect.

 

I found the problem, I had a pin connected incorrectly. I may have mentioned earlier that I don't have a lot of experience building circuits. It is working fine now.
I really appreciate all of your help Mike. Thanks again!

 

And thanks to all the others that helped also!

 

BTW the slope is right on both with the 9 V battery and now with a 12V power supply. At pH 6.0 (600 mV input, 2.14 V output) and at pH 9.0 (900 mV input, 3.21 V output).