[Floreaa]

Yesterday, I had some fountain-pen ink on my fingers. As I was using sodium hydroxide to ease the flow at the used water drain, I accidentally spilled some onto my hands, over the blue ink. Almost instantaneously, it turned crimson red.

I tried to find out what the ink was made of, in order to determine the reaction that occurs, but I didn't find anything on the Internet.

Anyway, I know some details about both the ink and the reaction, and I have some photos taken afterwards when doing the experiment properly. The ink was Schneider (just in case any of you knows the composition   ). The pH (measured by me with litmus paper) of the ink was around 6.5 and that of the final product was about 13. The sodium hydroxide was 50% in the solution. It also contained NaClO. Here I have some photos during the experiment (on my blog: dailychem.blogspot.com).

In conclusion, if any of you happens to know what is going on over there, please tell me your opinion here or on my blog. Thank you in advance.  

[Grundalizer]

Hey, looks like a really nice blog, especially for someone so young!  Keep up the good work.  I have to say though, a lot of the pictures up there are broken and do not show, like the ones about the ink, I can't see them. 

[tmartin]

I'm being a little lazy here, I should check my old lab notebook from when I TAed an analytical class; however,  I believe one of the independent experiments was along the lines of a pH dependence of a commercial dye/ink.  The UV spectrum would shift depending on the pH.  I also think that there are dyes that are pH dependent (a quick Google search at least made me believe I am not crazy).

My guess is that the NaOH deprotonated some functionality of the dye (guessing an alcohol, maybe not though, I don't know the structure of the dye) and either reacted somehow or formed the tautomer, changing the conjugation of the dye.  This tautomer could absorb a different wavelength of light, hence the color change.  I guess an easy way to test this would be to take some ink, treat it with some more NaOH, then treat it with an acid.  If it changes back to blue perhaps there is indeed a pH dependence.  Of course if that doesn't work, maybe the NaOH just ripped apart the ink and the color change was a result of decomposition.

[Borek]

I also think that there are dyes that are pH dependent (a quick Google search at least made me believe I am not crazy).

Any doubts?

http://www.titrations.info/acid-base-titration-indicators-preparation