sodium hydroxide measurement.

[corinth]

I have a couple of questions concerning adding sodium hydroxide to my sample in order to read the 8.2 on my ph meter.

Question 1. As I get closer to thee 8.2, I slow the drops of sodium hydroxide to read the 8.2.
A. from what I have seen on several You tube and information that I have read . they either state that I measure based upon the plunder(top of little mountain) on my plastic syringe while others say I should measure at the base of the plunder where the it meets up with the ml line.
B. It appears that there would be a difference in my final numbers or am I overthinking the matter.

Question 2. Does the method matter.
A. one website stated 15 ml sample in 20cc of distilled water. Another said 5 ml sample in 15 ml distilled water and yet another said 10 ml of wine in 50 ml of distilled water. does oit matter

Question 3. what frormula should I use to give me my results.
A.if I am using sodium hydroxide .02. do I multiply the amount of sodium hydroxide used to reach 8.2 by 1.5?
B. If using sodium hydroxide .01, do I multiply the amount of sodium hydroxide I use by .75?
C. Another video showed multiplying the amount used by 2, such as 3.6 x 2 -7.2?

I am confused

 

[ibglowin]

First off you should be measuring at the flat portion of the top of the plunger and not the center peak top of the plunger.

then

TA = 75 * V * C/S

Where: V = volume of sodium hydroxide needed to reach pH 8.2

C = concentration of sodium hydroxide used (0.1 normal or 0.2 normal)

S = volume of the sample of must or wine

For example: you have a 15 ml sample of wine and add 12 ml of 0.1 normal sodium hydroxide solution to reach pH 8.2

TA = 75 * 12 * (0.1 / 15)
= 6 grams/liter or 0.60%

 

[cmason1957]

That formula works out really well, if you use 0.2 N and 15mL of liquid. So, you end up with

TA = 75 * (0.2 / 15) * V = V

Everything else drops out.

 

[mkjennison]

As long as you take your beginning measurement and final measurement the same way (top or bottom of plunger), it doesn't matter where you measure from. However, it is best to measure from the outside of the plunger (where it meets the barrel).

The volume of sample does not matter, provided you do the calculations correctly. As stated above, easiest for 0.2N NaOH is using 15mL of wine sample.

The amount of distilled water you add IN THEORY should not matter. And, for these applications it will not. However, I know that adding excessive amounts of water can skew the titration (slightly) as well as dilute your phenolphthalein indicator. Too little water will make it hard to read the indicator through the wine sample for dark wines. So take those volumes of water as suggestions, and dilute your sample until it is rose' in color (pinkish) if you're doing red wine.

 

[mkjennison]

Oh, sorry. You're using a pH meter, not an indicator. Disregard what I was saying about the indicator.

 

[corinth]

Sodium hydroxide measurement

Thank you all so much. Now I will add all your info to my notebook.
What is the difference between .01 and .02 solution other than the obvious. One winemaker I talked to said that home winemakers use .02 while commercial winemakers use .01 more? Lastly, I have seen many advertisements from a number of chemical suppliers that sell the .01. Is it all the same?

Corinth.
ps: I just ordered a couple syringes which are more accurate than the ones I have.
pps: Plunder? I guess every part of every piece of equipment needs a term to define it!

 

[ibglowin]

0.2N NaOH is 2X as strong as 0.1N NaOH

You have to be more careful with 0.2N NaOH as you can overshoot the titration a lot easier since its 2X as strong. I myself prefer the 0.1N and that is what is supplied by several of the online sources. There are exceptions obviously.

 

[WI_Wino]

I just have to say I love this forum. I bought some 1N (not .1 or.2) from Midwest supplies on sale ($4 for 100 ml). This and some other threads I found during searching helped me figure out how to dilute it and use it for acid testing.

 

[corinth]

IBglowin, using the formula posted above "For example: you have a 15 ml sample of wine and add 12 ml of 0.1 normal sodium hydroxide solution to reach pH 8.2

TA = 75 * 12 * (0.1 / 15)
= 6 grams/liter or 0.60% "

If I were to use 0.2 solution, what would change in the equation beyond the obvious of 0.1/15 to 0.2/15 or would it?

Also, I saw a formula which used 1.5 rather than 75. I am confused!
thanks,
Coirinth

 

[ibglowin]

If you use 0.2 instead of 0.1N your amount of NaOH will be ~ 1/2, everything else being the same.

The 1.5 formula only works with 0.1N NaOH and a 5ml (wine) sample size. You asked for a formula that works for all of the possible variables and I gave that to you.

 

[SBWs]

A post on my BLOG about testing acid with a pH meter and the how's and why's. I tried to explain the formula as best as I could. The easiest way is with a 15ml sample and 0.2 NaOH because the amount of NaOH used equals the acid, no figuring required.

 

[corinth]

sodium hydroxide measuremeny

]I have found what all of you have stated to be very helpful. For this beginner, I read and then take my notes and get an "aha" every so often but then, I also find new questions as your answers give rise to new thoughts. I am used to that.

SBWs,
I clicked on the link. Wow, very well done. Since I am a visual learner and ex-teacher, the use of color to help us differentiate one part of the formula from the next was very impressive and effective.

I have never seen a formula for fruit wines (malic acid). Very informative.

I also included am interesting article taken from the fine vines on acid testinghttps://www.finevinewines.com/Acid-Testing-Article.html

And one more on you tube(this one is not as impressive)
[ame="http://www.youtube.com/watch?v=XstQOtL3H8E"]http://www.youtube.com/watch?v=XstQOtL3H8E[/ame]


Thank you,
Corinth