Any Hazards of Mixing Catechol in Hot Propylene Glycol?

[j_landecker]

Having mixed small Pyrocat test batches in PG, the PG starts to give off a bit of vapor when it gets around the 150-160F mark. This led me to wonder - how much Catechol is also going into the air as vapor at that temp, creating possible inhalation or eye absorption hazards? I usually wear a respirator but not eye protection at that stage (and don't put my face directly over the beaker!).
Thanks,
Jim

 

[Tom Hoskinson]

If you heat straight propylene glycol to 160F it will give off some water vapor.

No Catechol vapor is given off during mixing that I can detect. IMO there is no reason to use temperatures in the 140F-160F range. I start out with the propylene glycol around 120F. with continuous stirring.

I only increase the temperature if the components are difficult to dissolve.

 

[Gerald Koch]

Catechol does have a significant vapor pressure at room temperature, it boils at 245 C. Adding it to a hot solvent will only increase the amount that is released into the atmosphere.

I would suggest adding the catechol to cold propylene glycol and if it doesn't dissolve after a few minutes then gently warm the solution with stirring. If this doesn't result in full solution then repeat the gentle warming/stirring cycles until it does.

Catechol is should be treated with some respect as it is more toxic than hydroquinone.

 

[gainer]

I agree. I would rather not add anything to any hot solvent unless I have knowledge that it is safe. Catechol is pretty soluble in the glycols. Heating and stirring speeds up the dissolving process partly by reducing viscosity and increasing molecular motion.

It's strange how much can change about a chemical with only a change in position of one OH group. Color of stain, toxicity, smell, what else? And it's all mostly combinations of carbon, hydrogen and oxygen. A little nitrogen helps. It's a shame we cannot just throw the proper proportions of the elements in the pot and have a developer result. We already have hydrogen and carbon in pure water, and nitrogen is dissolved in aerated water. Why wouldn't that develop film? OTOH, who would want to drink developer? Well, maybe I do every morning, but I have to add coffee extract to it.

 

[Jordan]

I think that using eye protection is more important than using a respirator in this case.

 

[Gerald Koch]

It's strange how much can change about a chemical with only a change in position of one OH group. Color of stain, toxicity, smell, what else? And it's all mostly combinations of carbon, hydrogen and oxygen.

Another result of having the two OH groups adjacent to each other is that catechol forms a complex with borates that seriously reduces its developing ability. However, it has been cited as useful in the Peckham Catechol developer, BJ Dec 26, 1969.

It's a shame we cannot just throw the proper proportions of the elements in the pot and have a developer result.

You don't know how many times I've wished this. It would be a great way of obtaining developing agents like Atomal that are no longer made.

 

[john_s]

I've mixed up a few of the recent formulas using propylene glycol or TEA, and I've always been really reluctant to heat developing agents more than absolutely necessary. I can't remember which developer it was, but I avoided heating to the level recommended by just allowing the dissolution to take place over a few days in the boot of the car (I drive a lot) in warm weather.