Well, I realized I might give it a try and I need to confirm some ideas. I know blue.magic is using this technique, so he is the main target of this post, but maybe others can provide some info as well.

So let's say we would like to use nitrazine yellow for titration. I have seen that 0.4ml of 0.2% solution is used for 200ml of distilled water. So my questions :

1. If I buy 1g of nitrazine yellow and dissolve it in 500ml of distilled water, I get 0.2% solution I can work with, right?
2. Is the 0.4ml of 0.2% nitrazine solution advised for 200ml of water, so for every 100ml of water there is supposed to be 0.2ml? Or how is the amount calculated?
3. Is it problem if more nitrazine than advised is added?
4. Are there any cases of problems with this technique? Some chemicals interfering with it, causing it useless or anything similar
5. I believe nitrazine is removed while doing acetone washes. So "other alkaloid extract" for mescaline extraction is contaminated and useless, right?

Thanks!

Yes. I use dropper bottle so I dissolved 200 mg in 100 ml.

I haven't found any degradation when kept in solution for 6+ months.

The color range of nitrazine disodium salt (the Nitrazine Yellow) is as follows:

6.0 Yellow
6.2 Yellow, slightly duller
6.4 Pale yellow
6.6 Pale gray
6.8 Pale blue
7.0 Blue

Source: Wenker, Henry. "Nitrazine Yellow, a new indicator." Industrial & Engineering Chemistry 26.3 (1934): 350-350.



You don't have to be precise about that. The dye is very strong and just few drops per 200-250 ml water will suffice. Just enough to see the coloring. If the water is cloudy, more is needed but this is not the case with mescaline titration.



No, it will just dye the water stronger.



I don't know of any I used the indicator in several strong acids and bases and it simply colored the solution accordingly with no degradation observed.



I put few drops of acetone from freshly opened bottle (< 0.5% water) and almost all of it dissolved readily, leaving only few specks behind that did not dissolve even upon agitation. That might have been crystals or impurities, I am not sure, but given the dilution factor, the residue should be negligible (sub microgram amount even per high dose of extract).

I have not found any related health problems, the MSDS does not specify any hazards except for skin irritation when pure and possible explosion hazard (only when pure and heated).

I won't be concerned much since phenaphthazine (nitrazine) papers are used for vaginal pH tests by directly applying them on tissue in the birth canal.

blue.magic, thanks a lot for your entry. I discovered nitrazine thanks to you and now I can't believe I could have been without it! It is really very good technique!

Some experience ... there is a slight problem with nitrazine used within erlenmeyer flask for titration when the same water is used for all pulls. I am using just a bit of water, as there is no need to use much. Using more is not a problem, it just requires longer evaporation.
With so little water, it is very difficult to see the color of water layer, because it is the lower and thus thinner layer. For first pull, when the water is clear, it is quite ok, but for later pulls, when the water turns white, the coloration is much less apparent. I added some nitrazine, but it didn't help much.
So the result is : For titration with nitrazine - use more water and/or use separate water for every pull. Maybe different type of flask might help, though erlenmeyer is imo the best for this purpose