Hi. I just bought a pen-type pH meter. It doesn't say what brand it is anywhere, but the model is PH-03(I). Anyway, the people that sold it to me also sold me a bottle of "storage solution for pH and orp electrodes", a bottle of capsules that make a 7.0 pH solution, and another bottle of capsules that make 4.0 pH solution. They told me "there's instructions in there, it's easy". Well, I read the instructions and they are terrible. Could somebody please tell me what to do with the pills and the storage solution? Thanks in advance.
I'm just hazarding a guess, we use pen type meters at uni, You must constantly keep the electrode wet in the storage soloution. Also take care not to bang it. The capsules i'm guessing are to dissolev in water. You use these to calibrate the pen. Stick it in the pH4 solution first and make nessacary adjustments to calibrate it so it reads pH4. Then repeat with the 7. Rule of thumb: if your measuring a liquid with a low pH, its more important that your pH meter reads more accuratly at the pH4, than at the pH7. Hope this all makes sense!
I would not agree with that, pH is a log scale and both are important since you define the slope of a line with these adjustments. You usually set 7.0 first to define the 'zero' point and then do the other with most meters.
I would suggest that this either be returned to that seller or post a lot more info. I can post the pH FAQ again but it's here in the archives several times.
I agree you would add the pills to water, but there is no way to tell you how much.
If these are not pills but capsules about the size of a Tylenol extra strength caplet and are green and the other orange they sound like Hydrion brand capsules. You would take them apart carefully and add them to 100 ml of distilled water to make your buffer solution. They should have given you a small bottle of iodine solution too if so, that tints the solution so you don't mix them up but more importantly acts as a preservative; they will last 2 months with that in there if tightly sealed.
Thanks for the replies. One thing that I'm confused about: if pH 7 is neutral, then why do you need a capsule? Why can't you just stick the electrode in pure distilled water, which already has a pH of 7?
Also, if the pH meter only has one screw for calibration, what good is it to calibrate it with a pH of 7 and then with a pH of 4? I mean, with only one screw you can only calibrate one point. It will either be accurate at 7 or at 4, but not necessarily both.
Shows you are thinking, Franco. In this case, your assumption is incorrect.
Distilled water is not pH 7. The carbon dioxide from the air comes to equilibrium in solution, lowering the pH to someowhere in the pH5 to pH6 range, an unpredictable number.
The whole idea of the pH solution is the buffering effect; to keep the pH where you want it regardless of all other contributions to pH.
Even these buffered pH solutions 'die'. Their buffering capacity gets used up over time. That's why Storage life of a week or two in a partially filled, closed container or up to 2 months in a full, sealed container is a good rule of thunmb.
Newsgroups: rec.crafts.winemaking From: "Joe Sallustio" - Find messages by this author Date: 20 Jan 2006 03:09:19 -0800 Local: Fri, Jan 20 2006 7:09 pm Subject: Re: I need help on how to use a pen-type pH meter Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse
I would not agree with that, pH is a log scale and both are important since you define the slope of a line with these adjustments. You usually set 7.0 first to define the 'zero' point and then do the other with most meters.
I'm aware that the pH scale is logarithmic. I did not mean that you completely ignore calibrating at 7 if you intend to use it for low pH, i was merely stating that for all intensive purposes, you will find that once you calibrate to pH4, the metere will not read exactly 7, everytime. So if you are measuring at lower pH's its important to have the meter calibrated lastly to pH4.
I think returning it to point of sale for refund is a bit drastic.
At the end of the day, as long as you ensure you follow the same guidelines every use, at least you will be accurate if not precise.
I follow you but it's normal to set zero at pH7 and span at 4; only really old pH meter have only one adjustment (at least in my experience.)
Following up on your idea though: He could make a saturated solution out of cream of tartar (just add enough to distilled water that some does not disolve). That is a pH of 3.55, which is a nice value for a winemaking checkpoint. Cream of tartar is available everywhere.
DrinksForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.