Benzotriazole - Recrystallizing

[focus_on_infinity]

I made up a solution of 2% Benzotriazole around 2 months ago. It dissolved well enough into distilled water at around 190F IIRC. Since, it has been sitting in a full, tightly capped bottle on my shelf at around 64F. I went to use it the other day, and I found that the benzo has been recrystallizing into long, thin fibers, and has become a mass of hair, taking up a good deal of the bottle. I shook it up a bit, but from the looks of it I doubt it's going to go back into solution without some heat.

Is this normal(ish)? Did I do something wrong? Can I just heat and remix? I'm surprised, because the whole thing seemed to be going well.

 

[Wayne]

I use propylene glycol and never had a problem. It lasts for years. Don't know about water.

 

[GLS]

Benzotriazole has only sparing solubility in water, so yes it is normal that at certain concentrations it will crystallise out over time. Re-warming it to get it to re-dissolve shouldn't do any harm. As Wayne said, glycol solutions should keep more or less indefinitely.

 

[mrosenlof]

Wayne, do you need to heat the glycol to dissolve the Benzotriazole?

In the past I've dissolved it in denatured alcohol. I'm not currently using it.

 

[Wayne]

My solution is so old (over a decade) I don't even remember, but I very much doubt that I had to heat it.

 

[Patrick Robert James]

The last "fluffy" batch I got from Formulary wouldn't stay in solution. They changed to a more pellet form with the last batch I ordered but I haven't mixed it yet.

 

[Nicholas Lindan]

I mix up a 10% solution in 91% isopropanol.

Benzo makes a very good treatment for raw metal before painting. Really helps the paint stick. Endorsed by the US Navy...

 

[focus_on_infinity]

I use propylene glycol and never had a problem. It lasts for years. Don't know about water.

You dissolve it in pure propylene glycol? Or do you add it to water?

 

[Wayne]

You dissolve it in pure propylene glycol? Or do you add it to water?

Straight glycol.

IIIRC...

 

[focus_on_infinity]

Straight glycol.

IIIRC...

Cool. I'll give that a try. I think I have enough Benzo to last me until the sun burns out, at which time, I'm going to quit photography.

 

[gordrob]

I mixed up my benzotriazole in a 1% solution - 1gram to 100ml of 99% Isopropyl Alcohol. The BZT is not easy to mix in water and in some previous posts the use of denatured alcohol was not recommended because of the additives in it. I still have about 250cc left in a bottle that I mixed up 7 or 8 years ago and is as clear as when I mixed it.

 

[john_s]

It is more soluble in alkaline solutions. I have read that even sodium sulphite is alkaline enough to assist. It can withstand some heat to assist redissolving. It is used as a permanent conditioner for boiler water.

 

[Wayne]

I've used isoprp

It is more soluble in alkaline solutions. I have read that even sodium sulphite is alkaline enough to assist. It can withstand some heat to assist redissolving. It is used as a permanent conditioner for boiler water.

How much should I add to my boiler system?

 

[focus_on_infinity]

The last "fluffy" batch I got from Formulary wouldn't stay in solution. They changed to a more pellet form with the last batch I ordered but I haven't mixed it yet.

This is new stuff from the Formulary.

 

[Wayne]

Weird. Its always been pellet when I bought from them, but I don't think I have bought any in well over a decade.

 

[john_s]

I've used isoprp


How much should I add to my boiler system?

I mentioned that in order to suggest that heating it to redissolve would not hurt it, unlike, for example, developing agents which can be damaged by heat.

 

[Wayne]

I mentioned that in order to suggest that heating it to redissolve would not hurt it, unlike, for example, developing agents which can be damaged by heat.

Serious question. I have to buy all sorts of expensive anti-corrosives, scale and sludge conditioners with closely guarded recipes for my wood boiler and figure I could save a lot if I knew the recipes.

 

[pentaxuser]

.

Benzo makes a very good treatment for raw metal before painting. Really helps the paint stick. Endorsed by the US Navy...

If it increases stickiness and endorsed by the Navy then that will be why we Brits call sailors "tars"

pentaxuser

 

[craigclu]

1% solution in isopropyl (100%) has worked well for me. For my duties the smallish quantities used are easier to control with the weak dilution.

 

[focus_on_infinity]

Pfft, Ert, Urrgh. So, I redissolved it last night, and it went right back into solution with a little heat and stirring. And today it was a mass of hair again. I guess, since my glycol didn't arrive today as it was supposed to, that I'll try dissolving it again in the water for longer, just because I have nothing bettter to do.

 

[john_s]

 

[john_s]

The post above I copied from a web site years ago. Incidentally, I'm not sure that the figure quoted for solubility in pure water is correct.

There was a product in the USA (?Orthazite?) which was a solution of benzotriazole made soluble with, I think, sodium sulphite, which is apparently alkaline enough to increase the solubility. A bit of alkali won't do any harm in the normal photographic use of BZT.

For the OP, maybe heat to dissolve, then double the amount of water. It will probably stay in solution then.

 

[focus_on_infinity]

Interesting. This is very useful. I'll probably just decrease my wt%, as you say, since the volume of solution would be negligible for my purposes.

I did reheat and stirred more thoroughly. As of this morning, it was completely dissolved. However, just a few hours later, it had recrystallized even more completely than before. I'm going to hazard a guess that the liquid that is in the bottle is as saturated as it can possibly be, given the temperature and purity of the water that I'm using.

I got my propylene glycol in today, but this is just interesting trying to figure out how to do this with plain water.

 

[BAC1967]

Just had my Benzo go fuzzy, barely lasted over a week. I followed the directions on the bottle I got from photographers formulary. I mixed 10 grams into 500 ml of hot distilled water. I ordered some 100% propylene glycol, do I just do the same mix, 10 grams into 500 ml of propylene glycol to get the same results I was getting with it mixed in water? I assume propylene glycol doesn’t affect the development. I’m using it to reduce fog in some expired film.

 

[Murray Kelly]

Sodium bicarb has a pH of 8. You could add a pinch of that
Antifreeze (ethylene glycol) has BTA to prevent iron and copper corrosion. Premixed ?