The color of dry pyrocatechol

[Dennis]

I have just bought a supply of Pyrocatechol from one supplier that had to back order part of the order. The first part is a milky white color in the dry form. The second batch just arrived and it is a medium grey color maybe just lighter than a grey card.

Should I be alarmed at this? Is the darker stuff old? Should I expect the activity to be the same? Should I mix it all together and have a large batch that is all half dark half light? Really odd. I don't know what to think.
Thanks
Dennis

[Ken Lee]

Sounds like what mine looks like: light brownish-gray flakes.

That's what it looked like when it arrived, and it looks the same today, a year later. I store it in the plastic jar in which it came, with the lid closed.

According to http://www.jtbaker.com/msds/englishhtml/p7896.htm (see item 10) it "discolors on exposure to air or light".

I just mixed some developer using it, and the results were just fine.

To get it really fresh of course, we could always make our own.

According to http://en.wikipedia.org/wiki/Catechol

Catechol is produced industrially by the hydroxylation of phenol using hydrogen peroxide:

C6H5OH + H2O2 → C6H4(OH)2 + H2O

[Scotty230358]

Mine is a very pale biscuit colour and works fine.

[sanking]

Pyrocatechol when fresh is slightly off white, just a tad toward a light tan. As it ages it gets darker and eventually will get dark brown. But with good storage this should take a very long time, over three to five years in my experience.

By the time it gets dark brown it will have lost over 50% of its working strength and while it may still work you would need to adjust the formula by adding more of the pyrocatechol. But so long as it is no darker than light, medium or dark tan it should be ok.

Sandy