Testing kit acid, huh?

[koomber]

Annnnnnny way, I kinda lost track of my point.
The point was that the vinoferm kit can be used for SO2 testing purposes whilst the phenophthalene kit cannot. I'd also wager that the phenophthalene based kits are more accurate with respect to wine acid, although because the wine acid test is very complicated (titrating against 3 acids in a wine versus 1 acid in SO2) it might not be significant.

Organic acid titrations are complicated. If I get some time I'll try and do some titrations to some known volumes in the lab.

On a slightly related post, if you are buying phenophthalene, the cost of the powder is about £6 for 50g from Alfa Aesar (product code A17135) and indicator solution is about a 1% dilution of the powder in methanol, or indeed any alcohol would work.

[koomber]

I was looking for the instructions for the Vinoferm Acid test kit .

I'm curious because of the indicator in the Vinoferm kit is most likely Bromothymol Blue. Actually the whole fluid, is really bromothymol blue and the base mixed in. This way you only add in one chemical.

Anyway, my point is that they change colour at a different range:

Bromothymol Blue: 6.0–7.6
Phenopthalene: 8.3–10.0

Because of the nature of the tests and the what you are measuring when you do a pH titration. Basically you are looking for the midpoint where the pH changes from being acidic to basic.
The colour change of the indicator you are using should occur so that the midpoint of the pH levels happens during the colour change. Obiously, this cannot be true for both the indicators...
Whether they will be different enough to affect the flavour is a different matter though...

[SiSandrine]

Don't suppose you have a copy of the instructions? I'd be interested in seeing what they say. It would allow me to work out what is in it too. If it's easier to use the Richies I'm sure a heap of folk will be interested.

What is the colour change in the indicator?

Hi Graham,
Not sure if you were asking for this but in case you were.
Boots Caustic Soda is 98% Sodium Hydroxide which I reckoned to be pure enough and took 4 grams of it and added 1 litre tap water to make up the 0.1N NaOH.
To test it was working I then took 42grams of Citric Acid and added 4.5 litres of water (1%). I did this by weighing rather than relying on measuring jugs etc. 5ml of this should give a TA of 6.6 (or 6.5 as my syringe likes to call it).
Phenolpthalein I bought from Loire Viti-Vini Distribution - as I said I will be going back in August so can pick some more up. I think it was about 3 euros for what looks like 75ml. It dyes very bright and obvious purple.
I also bought a litre of distilled water and use a jam jar for a test tube. That way with my 5ml of red wine I just add loads of distilled water and colour change is really easy to see.
Test with the citric acid solution was spot on 6.5 TA.

Boots Caustic Soda - £2.50 for 500grams
Phenolphthalein - £3.00
Distilled Water - £3.50
+ 42 grams citric acid + tap water + used jam jar (well washed).
This gives me a lifetime supply and really easy acid measurements.

Actualy just checking I mentioned this before - inckuding all health warnings - see below.

http://www.winesathome.co.uk/forum/showthread.php?t=4749

[robwrx]

Hopefully this works, this should be the instructions for the Vinoferm Acidometer.

[lockwood1956]

A link to Lucs blog is ok....however he doesnt want any of the content "cut and pasted"

some great stuff on Lucs blog, he has done some very interesting experiments.

good winemaker...great guy (he visits here regularly as a guest)

[robwrx]

Don't suppose you have a copy of the instructions? I'd be interested in seeing what they say. It would allow me to work out what is in it too. If it's easier to use the Richies I'm sure a heap of folk will be interested.

What is the colour change in the indicator?

I will scan the instructions and post them later.

The indicator is a dark blue chemical and the wine or must goes from yellow to green at the neutral point.

I found out about the Brouwland kit on Luc Volders blog which includes some very good tutorials. I hope it is ok to post a link to it.
http://wijnmaker.weebly.com/english-start.html

Scroll to the bottom for the English translation.

Rob

[Cellar_Rat]

here we go..

[Cellar_Rat]

I have the Richie instruction somewhere - I will have a dig

[koomber]

Don't suppose you have a copy of the instructions? I'd be interested in seeing what they say. It would allow me to work out what is in it too. If it's easier to use the Richies I'm sure a heap of folk will be interested.

What is the colour change in the indicator?

[robwrx]

Brian, I wasn't adjusting the acid in a kit, just testing it to get in some practice with a new toy.

Simon, I have a richies test kit but A, I find it a fiddly thing to use with test tube and syringe and B, understanding and adjusting sulphuric seems overly complicated. I can understand percentages/grams per litre so much easier. Maths never was a strong point.

Brouwlands acid test kit is a pleasure to use after many months of faffing, no distilled water, no syringe and only one bottle of chemical to worry about.

[SiSandrine]

Also I find the Ritchies kit method pretty good for getting accuracy. That said I replaced the chemicals by making up my own 0.1n NaOH using Boots Sodium Hydroxide (Caustic Soda) and checking the accuracy using a citric acid solution. Checking with Koomber all the way of course
I also bought a new jar of Phenypthalein from a professional wine supplies shop in Vallet (near Nantes, France) which seems to be much clearer (a shade of purple) than the stuff that comes in the kit. If anyone wants any I'll be going back in August so can pick some supplies up if any use.
I also use a jam jar for a test tube and use lots of distilled water to dilute which makes the colour change to purple in reds really easy to see.

[Cellar_Rat]

I have to question why you are adjusting the acid (or thinking about it) it a kit wine?

[robwrx]

Thanks for reply bzac. I have tested a couple of commercial wines and got the sort of results you would expect but they are finished wines. I want to be able to reliably test and adjust the acid content of the must prior to fermentation. As you suggested I need to buy a few bottles for research purposes

Rob

[lockwood1956]

" but dear its for research!"

lol

love it.

[bzac]

kits are very buffered and are also designed to be drank young so there may be some weird test results (due to low acid levels) .

I would try practicing a couple tests out on commercial wines . gives you an excuse to buy some, " but dear its for research!"