The Blues.

[nigelb]

Try using less IPA. In my soap test tutorials I only used 50ml. 100ml is such a waste. Its only there as a carrier. Also what % is your bromophenol blue?

[DavidA]

0.04% as is the Bromothymol blue.

I agree it is very wasteful, but I was following Graydon Blair's instructions as shown in the wiki.

I wasn't sure if it was necessary to use so much to get a quantitative measurement of the soap from the amount of 0.01N HCL used in the titration.

I would be much happier using, say, 25 mL if it will yield the same result.

IPA isn't cheap.

[nigelb]

You need the bromophenol blue to be 0.4%. Thats why its not making a jot of difference to a colour change to the IPA

[DavidA]

So, ten times stronger.



Time to go internet shopping again.

Thanks for that

[nigelb]

Its all in the wiki under soap testing.

[DavidA]

Where do you buy your 0.4% Bromophenol blue ?

[nigelb]

I used to buy it from a lab supply buisness in Atherstone. Not sure it's still there. I used to deal in soap testing...but i've only got 30ml left.

[countrypaul]

Try the obvious first, use 10 times as much indicator as you have tried. Given the small overall amount in 100ml of ipa using 10 times as much should not have any adverse effect.

[DavidA]

0.4% Bromophenol seems very expensive (and hard to come by).  I may try a compromise and get some 0.1%. It's cheaper may work.

For the time being I'm going to run a few tests using Bromothymol blue as I have about 500mL of that.

I'll hold back some of the bio I use so I can compare the results with the Bromophenol blue when I get some.

A quick tip.
I found that the 1 mL syringes you can get from the pharmacists will, if you cut of the little 'wings' at the top, fit neatly into a two mL pipette pump. And they are only 50 Pence each.

[DavidA]

A quick question.

How much soap would you expect to find in unwashed bio ?

My test sample shows (apparently), 100 % conversion; 1 litre of oil in, 1 Litre of bio out.

The byproducts equal the total Methanol I used.

I ask this because, as you know, I am doing some soap tests.

I have just watched the video recommended by the people who supplied my soap kit (Intelli-ink), and the guy there used 11 mL of 0.01n HCL to get a result of 3344 ppm.

Is this what I should expect ?

And would washing greatly reduce this figure to something nearer the ASTM acceptable 41 ppm ?

I has me wondering because I never used to do soap tests on my fuel, and it didn't appear to do any damage.

[nigelb]

Unwashed raw bio from my experiments can be as high as 13000pm.
Doing a post reaction wash will typically reduce it to 1300ppm.
There is some anacdotil info on testing on the vod.

Testing raw bio can take a heavy hit on your indicator and lab grade HCL unless you reduce the sample size and then multiply the result by the same factor.

[DavidA]

A very heavy hit indeed.

Looks as if it will soon be time to shift to doing micro-samples.

[DavidA]

Anyway, I got a result.
Here is the process.

10/90 test on bio showed no discernible drop out overnight.

Washed bio.
100 mL bio + 100 mL lukewarm water. Used Tilly method.

After seven wash cycles both water and bio passed the 'newspaper' test.

700 mL water used in total.

Soap test.

50 mL good IPA in 250 mL beaker on stirring table.

Blanking.  Three drops 0.1% Bromophenol Blue indicated IPA was alkaline.(Blue).

Two drops of .01 HCL brought it back to yellow.

Added 12 mL bio. Turned blue.

Titrated  0.230 mL  0.01 HCL to get back to yellow.

0.230 x 304 = 69.92 ppm.

That will do for me.

[dgs]

Good lad, I've always used about 17 drops of b ph b.

[DavidA]

I've used both and have both, there is very little difference. The soap test if done properly is about the quickest and most accurate of all the 'shed' tests. Make sure you blank off the ipa. With an accurate titration you can get a result of +/- 5ppm.

Just had an interesting( not to say frustrating) experience related to the above.

I was checking the soap content on my latest batch of bio. And couldn't get it to work at all.

It went ok until I added the oil. But immediately turned yellow instead of the blue I was expecting prior to adding the HCL to do the titration.

After three (yes, three) attempts it dawned on me that I was using Bromothymol Blue by mistake (It is in a similar bottle to the Bromophenol blue) .

The fourth attempt, using Bromophenol Blue worked out fine.

So, best avoid Bromothymol blue altogether.