I was gifted with a Hanna Checker at Christmas and am trying to get the thing to give me an semi accurate reading on TA.
So far I have used a method of 15ml acidic sample and added drops of .2N NaOH solution. By the time the sample reads 8.2 on the meter I have added only 60% of the expected volume of NaOH. Confused I created a sample of .5% tartaric acid ( 5g acid powder with enough water to make 1litre volume) and tested this control sample. I netted 4 ml NaOH instead of the expect 5ml. is this the
I always use the .1N NaOH solution, but my supplier sent me the .2 solution and I asked for directions for how to use it. These are his directions.
Start with 15 ml of the must.
Drop 3 drops of the phenolphthalein into the 15 ml must.
Measure 10 ml of sodium hydroxide.
Add sodium hydroxide to the must in quantities of .5 ml at a time, swirling to mix well after each addition. Watch for color change in the must.(Or PH reading on meter.)
When the entire sample has changed color (Pink for white wines; gray-green for red wines.) you need to stop and see how much sodium hydroxide you have used. (Be sure to subtract what you HAVE LEFT from what you STARTED with to get how much you USED.)
The amount of sodium hydroxice used (i.e. 6.5 ml) is the same value as the TA (acid) concentration of the must in grams per liter (i.e. 6.5 grams per liter). This might also be expressed as a percentage of weigh to volume .65% meaning 6.5 grams of acid per 1 liter of must.
You may also add distilled water to dilute the must to help see the color with red wines if you like. This should not be necessary with the PH meter. Also one very important point is that your sodium hydroxide solution must be fresh. If is six months old or has been left open for extended periods of time, it will loose it's strength and give a bad reading. Hope this helps. Aubrey
I always use the .1N NaOH solution, but my supplier sent me the .2 solution and I asked for directions for how to use it. These are his directions.
Start with 15 ml of the must.
Drop 3 drops of the phenolphthalein into the 15 ml must.
Measure 10 ml of sodium hydroxide.
Add sodium hydroxide to the must in quantities of .5 ml at a time, swirling to mix well after each addition. Watch for color change in the must.(Or PH reading on meter.)
When the entire sample has changed color (Pink for white wines; gray-green for red wines.) you need to stop and see how much sodium hydroxide you have used. (Be sure to subtract what you HAVE LEFT from what you STARTED with to get how much you USED.)
The amount of sodium hydroxice used (i.e. 6.5 ml) is the same value as the TA (acid) concentration of the must in grams per liter (i.e. 6.5 grams per liter). This might also be expressed as a percentage of weigh to volume .65% meaning 6.5 grams of acid per 1 liter of must.
You may also add distilled water to dilute the must to help see the color with red wines if you like. This should not be necessary with the PH meter. Also one very important point is that your sodium hydroxide solution must be fresh. If is six months old or has been left open for extended periods of time, it will loose it's strength and give a bad reading. Hope this helps. Aubrey
Don't take this wrong, but the worst pH meter I ever used was a Checker, the probe on mine was horrible. Others have had better success.
I sent it back and upgraded to a better Hanna meter. I realize yours was a gift, but I have a lot of experience in measurement and control and would not recommend the Checker.
Hanna makes the pHep 3 and the pHep 5; you may have much better success with one of those. I have both and have no complaints on either. The pHep5 gives you the most bang for the buck, the design is newer.
Strange, I wouldn't expect to see this much difference. Repeat with colour indicator, just to check the pH meter. If there's still such a difference then it seems the acid powder is far less pure, or the NaOH is too strong! A 60% purity of acid would be absolutely terrible, my tartaric acid ('Shirley', UK) is near 100%, tested with the same procedure. 40% moisture in the salt is also highly unlikely. Is your balance for making the acid stock sol accurate enough??? (my most suspected guess); check with a pharmacist.
On a pure stock sol of acid, the +/-0.2 of the pH meter would at the most make one drop of NaOH difference (at pH 7 or 8)! I do not think the meter is the problem, but make sure the probe is stabilized anyway, if this is the first time you're using it. (Calibration?)
I have heard of people having problems with tapwater for dilution/stock sol, it can be alkaline (use boiled rainwater if no distilled water is available). However, the difference is too big to be explained by this effect; it wouldn't be fit for human consumption if it was...
5g tartaric acid in a graduated cylinder mixed with 500ml distilled(RO) water to dissolve and then topped up with more water to 1L. Checked on a gram scale which showed 1000 +/-1g
Fresh calibration solution was used to adjust the meter before starting the test.
I started with a Checker, and only because I saw the pHep5 advertised, I bought that as well. The pHep5, to me, was worthless. I would calibate it at 4.0, wait 2 minutes and then check my standard again, and it would register 3.85. This happened at a standard of 7 as well. There was simply NO consistency. Also, the numbers seemed to drift endlessly.
Finally, I simply bought another Checker, and I always double check each sample. The 2 checkers are always within .05 of each other.
So, to each his own. But I think the pHep5 is a piece of garbage.
That sounds like you've got one with a faulty electrode, you should be able to return it and get a good one. Overall, most people who I know who have pHep5 swear by it - that includes myself.
Sounds like a bad electrode or bad electrical connection to me, sorry to hear that. Electrodes are very high impedance and it does not take much crud to make them act up. My experience was the opposite, I had a bad electrode on the Checker.
Electrodes have a finite life but my pHep3 was at least 4 years old when I replaced it, it was still working fine. The pHep5 I have now is about 3 years old.
There are other vendors out there too, Cole Parmer sell Oakton pocket meters which are pretty decent too. I limit the cost to under $100 since I'm not using it for business, otherwise I would get a really good meter and probe.
I would have done the same thing if I were you, if it won't calibrate the meter is useless.
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