[Ballistic]

Hi guys
I mixed up some dyes for microscopy staining and was surprised to see some material drop out of solution. I'm not sure what proportion didn't dissolve and what proportion dropped out later with temperature changes. The main one I had the most material drop out was Methylene Blue (used in DNA staining).

I had originally checked that I could dissolve a 2% solution at room temperature however my store room is outside temperature (down to freezing point almost) and I haven't been able to find a graph of the solubility of Methylene Blue at different temperatures but the reason I'm posting is I can't imagine this curve would be so dramatic to cause half the material to drop out of solution as appears.

I did some google searches and one data sheet from one firm describes the material as containing x amount of "insoluble material". What would this insoluble material from one manufacturer of MB be? Assuming it's not contaminants, could the material just form clumps that are insoluble or are we talking at the molecular level?

Any random thoughts on this would be appreciated!

[Yggdrasil]

I haven't worked with methylene blue, but many dyes are quite flat and non-polar which makes it easy for them to stack together and aggregate in aqueous solution.  Here's a paper of methylene blue aggregation I found after a quick google search: http://pubs.rsc.org/en/Content/ArticleLanding/2000/CP/B005370H#!divAbstract

[Ballistic]

Hey thank you, "aggregation" got me looking in new areas of research.
I found that you can reverse aggregation simply by diluting, however I'm not sure that a very practical answer as I'm trying to create a set strength of solution the same as the original one that aggregated, (the original solution was made to a set percentage and the material aggregated out so what's stopping it happen again)?

I have yet to find out if raising the temperature or stirring, say with a magnetic stirrer, will aid re-dissolving the aggregated material?

Does aggregated material change in someway, e.g. diluting the solution or raising the temperature break down big clumps but leave groups of molecules aggregated?

[Yggdrasil]

What solvent are you using to dissolve the dye?  Most sources I find make 0.2% stock solutions in water, so a 2% stock may require a different solvent than water.

[Ballistic]

The solvent is water.

This source quotes the solubility as 3.55g / 100ml :     http://www.ihcworld.com/_technical_tips/solubility_chart.htm
Fisher make 1% aqueous solution
Here is a 1.5% solution classed as concentrate: http://www.sigmaaldrich.com/catalog/product/sigma/03978?lang=en&region=GB
This company was where I got my original 2% aqueous solution though they seem to have pulled it: http://apcpure.com