Solvents for phenidone, benzotriazole, ...

[bernard_L]

Two questions concerning phenidone, benzotriazole, and similar chemicals (any I forgot?) kept as a non-aqueous stock solution.

1) I've seen mentioned isopropyl alcool, propylene glycol, diethylene glycol (I leave out TEA, which is also a alkali). Any reason to prefer one for this or that chemical agent?

2) Apart from the convenience of measuring cc's from a stock solution instead of 1/10's of grams of powder, will the chemical agents be better preserved in the long term than in powder form?

Thank you.

 

[Wayne]

I've tried isopropyl and propylene glycol, and found the latter much easier for both phenidone and benzo-t. Its only slightly harder to find. I did not enjoy dissolving phenidone in isopropyl, from what I recall. I'll let the chemists answer the second question definitively but I've only noticed slight yellowing of my phenidone-PG stock over 5+ years in a clear glass bottle. I'll probably replace it now. I don't do it for storage longevity, I do it for ease and convenience and the fact it also lasts a long time is just a fringe benefit. AFAIK the benzo solution will last indefinitely, but I could be wrong.

 

[Gerald C Koch]

Benzotriazole is usually used as an aqueous 1% solution since it is 10X more effective as potassium bromide which is used as a 10% solution. This allows the user to easily gauge how much to use as they can be exchanged one for one. Since the solubility of benzotriazole is 2g/l there is no problem in making a 1% solution. Sometimes a bit of heat is needed for quick dissolving.

Any solvent should not react with what is to be dissolved. Therefore alcohols or glycols are usually used. Ethyl or isopropyl alcohol is a better choice since they do not evaporate as readily as methyl (wood) alcohol. Some people find viscous liquids like glycols hard to measure.

 

[john_s]

People's experience with phenidone in alcohol varies. Mine was not good, and I surmise that it was due to some water in the alcohol. It's apparently not easy to keep atmospheric water out of it even if it starts very pure, which mine wasn't.

 

[Gerald C Koch]

People's experience with phenidone in alcohol varies. Mine was not good,

Phenidone does not keep well even as a solid. The solid should always be stored in a glass container protected from light, air, and moisture. A better choice would be to replace it with Dimezone-S which keeps better. Phenidone is best added to developers as a solid which requires in most cases a scale with an accuracy of 0.1 g or better. Both alcohols and glycols readily absorb moisture from the air. When dealing with developing agents and their solutions glass is preferable to other container materials.