Acid test kit.

[Wally]

Is there a good way to test the accuracy of the acid test kit. I am doubting my results. I tested some fresh white grape juice and it took 1.5 ccs of the reagent to get to the color change. It is the cheap baker and crosby kit sold by Midwest supply. The instructions say for each cc to the end point indicates .1% acid which would mean the juice is only .15. And that seems very low to me. I thought about testing a little distilled vinegar of a known value, (5%). Does that seem possible. I would have to dilute the vinegar with water to get it to something like .5% in order to test it. I really would like to know the real acid content of the juice before I start the fermentation. Need some sound scientific advice on this.

 

[cmason1957]

I would think you could add a known amount of acid bleed to a gallon of water.

On a side note, it is probably better to buy a PH meter and use it for your avoid test, instead of the color change. Add acid, until you reach 8.2 on your meter. Why 8.2? That is when the color change happens.

 

[Wally]

Thank you for the idea, that makes more sense than diluting vinegar.

 

[Wally]

Well, I bought the Hanna checker ph meter. I went through the cal procedure which was frustrating because the reading kept changing for seemingly no reason. Very unstable. Finally got it to where I thought it was close. Then I tried measuring a sample of grape juice. Again the reading was very erratic going up and down between about 1.5 and 3.2 up and down, up and down. never really settling on a number. I am not happy. does anyone use this meter with any success? Maybe I just got a bad one.

 

[ibglowin]

I have had a Hanna pHep 5 for several years now. No problems, rock solid stable, very happy with it.

 

[JohnT]

How about adding .5 grams of tartaric acid to a liter of distilled water?

Wouldn't that read as .5 ta?

 

[chrisjw]

I also have the Hanna pHep 5 HI 98128. No problems here. I take care to store it with the storage solution with electrical tape wrapped around the cap seam. Sometimes it takes 30 seconds or so to stabilize but when it gets there it stays.

 

[Boatboy24]

Another pHep 5 user here. Seems to work well. It calibrated easily the first time and reads steady.

The second time, I couldn't get it to calibrate. Turns out it's because I took it right out of the storage solution and into the calibration fluid without rinsing. I'll be using it again tonight and will be sure to rinse prior to use this time.

 

[Wally]

After contacting both Midwest Supply and Hanna Instruments. I have the ph checker working as expected. Midwest agreed to let me send it back to them for a replacement. In the meantime Hana Technical services sent me a new electrode which fixed the problem. I can now give a hearty recommendation to both Midwest Supply and Hanna Insrtruments for their great support.

 

[ibglowin]

Great to hear on all accounts. Just an FYI, pH meters are finicky by nature, even the expensive ones ($2000) can be problematic. Treat them with respect and be gentle to them and they will (usually) reward you in kind.

 

[spaniel]

Makes sure you were mixing the juice adequately. You can get the color to appear very early if you don't mix and mix; when the solution is truly uniform it will go away again. Same with the pH reading.

If I were to splurge on an item it would be a magnetic stir plate so we could do it like I did in the lab back in the day.