Strange Brew.

[DavidA]

No, not the song by 'Cream'..

When I have done a 10/90 test I pour the contents of the (pointy glass vessel, I'm going aphasic) into a demijohn. There is about three litre in it.
The colour of the liquid is fairly clear. And it doesn't change with each additional 100 mL  I dump in it.

Until today.

Quite a while ago I did a test sample using a litre of new oil. It's a while back so I forget what the titration was. Anyway, it turned to jelly.

So I muttered a bit and just left it.

Today I noticed that there was a bit of glyc at the bottom, and a bit of bio at the top. So I did a 10/90. When I had finished I dumped the test products into the demijohn.

And a white cloud instantly spread throughout the stuff that was in there .

I now have a very pale white demyjohn of meth+drop-out oil.

What caused this ?

Dave.

[dgs]

An immiscible mixture of oil and methanol perhaps.

[DavidA]

Could be. There was a massive quantity of Methanol compared to the oil.
Anyway, it's starting to clear down.

Something different.

What is the correct way of ascertaining the quality of one's Isopropanol ?

I can check the specific gravity. But are there other methods ?

[countrypaul]

As Dave suggests an immiscible mixture, when you carry out a Warnquist test do you ever see a white solution before the oil separates to the bottom? What you have is probably the same thing on a larger scale. is there oil at the bottom of the demijohn? They cloudiness can also be caused by mono- and di- glycerides - so partially transesterified oil.

If you buy from a reputable seuuplier they should be able to supply you with a statement of quality (forgot the normal name) which should give you all you need. You can test the acidity of the IPA by titrating it with NaOH solution (it is normally acidic due to oxidation). Why are you wanting to check your IPA?

[nigelb]

I think you mean a C of A (certificate of analysis) or a C of C (certificate of conformity)

There is some dodgy shit out there on the net. A few years ago uncle h ( Chad) was having dificulty with my soap testing kits. I suspected a duff batch of ebay IPA. This was confirmed when I went over to his place with some of mine. It was contaminated with something that I couldn't detect. No strange odours or appearance issues!

[countrypaul]

I think you mean a C of A (certificate of analysis) or a C of C (certificate of conformity)

There is some dodgy shit out there on the net. A few years ago uncle h ( Chad) was having dificulty with my soap testing kits. I suspected a duff batch of ebay IPA. This was confirmed when I went over to his place with some of mine. It was contaminated with something that I couldn't detect. No strange odours or appearance issues!

Yep, I just couldn't remember the proper name for some reason 

[DavidA]

If you buy from a reputable seuuplier they should be able to supply you with a statement of quality (forgot the normal name) which should give you all you need. You can test the acidity of the IPA by titrating it with NaOH solution (it is normally acidic due to oxidation). Why are you wanting to check your IPA?

I was wanting to be sure that the IPA was in good condition. I did have problems a while back that turned out to be down to the IPA I was using in my titrations.

So, today I bought a small quantity of 99.9%(it says on the bottle) IPA. At 3 Pound Fifty for 250 mL it better had be good. 14 Pound a Litre !

Now I just need to know how to titrate a sample of it to be able to get meaningful results. The I can compare the results with the stock IPA I have.

Paul, dgs,

I quick tutorial would be useful. Which indicator etc.

[DavidA]

While watching a few videos on titration I see that the operator often washes the tip of the burette and/or the inside of the flask with distilled water during the process to ensure all the titrant is in the flask. Particularly any drop that may be clinging to the tip.
Does this mean that the distilled water will have no effect on the result ?

[countrypaul]

While watching a few videos on titration I see that the operator often washes the tip of the burette and/or the inside of the flask with distilled water during the process to ensure all the titrant is in the flask. Particularly any drop that may be clinging to the tip.
Does this mean that the distilled water will have no effect on the result ?

If you are doing a normal acid/base type titration distilled water should have no effect.

Where did you buy your IPA from? If it is a chemical supplier they should be able to supply a certificate for it as Nigel said.

[DavidA]

The IPA was bought from a local hardware store.

Propan-2-ol, CAS No:67-63-0- EC No:200-661-7

Bird Brand.

RK and J Jones Limited. Southerly Road, Feltwell, Thetford. Norfolk.

https://www.birdbrand.co.uk

Looks like a well established company. They do a range of solvents.

[countrypaul]

They have an MSDS on their website but I could not see a CoC  - that may not be surprising as I would expect them to buy in relatively small quantities for repackaging and own use so might be difficult to determine which batch an indiviual 250ml container came from (though not impossible assuming they record batch numbrs for everything).

The MSDS suggests 99.8% pure (rather than 99.9 initially stated) again that might well be within acceptable limits given the intended purposes.

I would be a lot more confident of that supply that an unknown Ebay supplier.

£14/L is not too bad for very small quantities, have a look here if you want to see what some of the higher spec stuff costs https://www.sigmaaldrich.com/GB/en/search/67-63-0?focus=products&gclid=EAIaIQobChMI44mE75eC-AIVDO7tCh0FtArUEAAYASAAEgI4HPD_BwE&page=1&perpage=30&sort=relevance&term=67-63-0&type=cas_number - yes that is nearly £100/L 

[DavidA]

I'll accept 99.8 as near enough as I want to do comparative tests with my stock IPA.

Just have to refine my titration skills now.

[DavidA]

One point.

Does 4 drops of 0.1 Bromophenol blue equate to 1 drop of 0.4 Bromophenol blue ?

[countrypaul]

One point.

Does 4 drops of 0.1 Bromophenol blue equate to 1 drop of 0.4 Bromophenol blue ?

If using it as an indicator yes.