Titration Question... one for the Chemistry Graduates

[Chalkyt]

A long and hopefully interesting story... and I have to say up-front, that chemistry isn't my long-suite.

In the past, some titration kits have been available in Australia. They come with the necessary bits, are relatively cheap (although not as cheap as in the USA), and easy to use.

However, we can't get them now because the chemicals (sodium hydroxide and phenolphthalein) have been classed as "dangerous" and can't be sent through the mail. So, getting replacement chemicals in small quantities is an issue.

I can get sodium hydroxide in dry and food grade form, but I would have to accurately measure exactly 4.0 grams of flakes or pearls and mix it in exactly one litre of water to make a 0.1N solution for titration. I have a good deal in place for this... in return for cider, the local pharmacy (Drug Store) will make up accurate solutions for me as they can weigh to 5/1000-gram precision.

With that issue solved, the problem now seems to be accessing phenolphthalein indicator. Phenol Red (as used in pool test kits) is readily available. Has anyone used this as an indicator for titration to determine the acid level of cider. If so, how does it change the procedure (if it does) i.e. is it the same. I am trying to put together some data about my apples to help with blending. SG and pH are easy, but TA needs titration. The apples should be ripe in a month or two, so this isn't super-urgent but it would be good to know what to do.

Any wisdom regarding alternative TA methods, indicators, etc, will be very much appreciated since all the information I can get seems to revolve around phenolphthalein as the indicator.

Cheers!

 

[Maylar]

Using an indicator sucks because your test subject might be colored. An alternative method is to use a pH meter, though I can't seem to find the directions. Basically, you mix up 25 ml the same as you would for the indicator, and add a drop at a time of the 0.1N solution until the pH reads 8.2. I'm sure you'd find this on the web somewhere.

 

[Willammes Macena]

Se quer apenas uma titulação simples com base no ponto de viragem confira se azul de bromotimol é viavel em seu pais

If you just want a simple titration based on the endpoint check if bromothymol blue is viable in your country

 

[bernardsmith]

Easiest method , though is a pH meter. You measure the chemical base Na OH you add drop by drop to a sample of mead or wine (Morebeer suggests 15 ml) and you stop when the pH hits 8.2. THAT is the precise point when the indicator would change color. Testing Wine Musts For Sugar, pH, and TA | MoreBeer

 

[Chalkyt]

Thanks for the replies. I had read about using a ph meter somewhere. I bought a cheap one some time ago but as I basically only using it once a year to measure pH and not for titration, the bulb dried out (even though it was stored in the appropriate liquid. The test kit indicator just seemed to be easier.

The local pharmacist also mentioned using a pH meter so maybe that is the way to go with a "proper" one.

The other issue is my confusion about the strength of the NaOH. One of the test kits that I had used 0.1N (4g/L concentration) and the other 0.2N (8g/L). I guess that the number of mililitres used to reach pH 8.2 will different but the More Beer instructions don't refer to which concentration they use.

 

[Chalkyt]

It seems that bromothymol blue is readily available here via ebay, and is sold as an indicator for fish tank management. So, is this a suitable direct replacement for phenolphthalein as an indicator? i.e. if I use this, is everything else the same as the Brewcraft and Cellar Science kits that I have used before (instructions, test sample, drops of NaOH, any calculation to convert to malic acid equivalent etc)?
Thanks to those who know more about this than me!