Preparation of Neutol/Adotol WA

Gast · 2010-02-22T12:27:22+00:00

Hi, in den Agfa-Unterlagen heißt es, man soll Neutol liquid WA mit 30°C warmem Wasser ansetzen, und dann zur Verwendung auf 20°C abkühlen lassen. Gilt das a...

Gast

Hi, The Agfa instructions say you should mix Neutol Liquid WA with water at 30°C, and then let it cool to 20°C before use. Does that apply to Adotol as well? Or does it not really matter, as long as you give the solution enough time to mix? So far, I’ve always prepared my Neutol with warm water just to be on the safe side; if you could skip that step, that would be something... :rolleyes: Regards, Matthias

Wolfgg

Hello Matthias! My original Agfa documentation on Neutol WA liquid (dated October 1970) makes no mention of a higher preparation temperature – and what chemical sense would that make anyway? Nothing needs to be dissolved any further; it just needs to be distributed evenly. Or is there a supersaturated solution when dealing with partial substances? In that case, partial withdrawals would be problematic and the instructions would at least have to state: “Stir the concentrate well before withdrawal”. But I’m not aware of anything like that. Just give it a go – perform the dilution at 20°C (I always use 20°C); a comparison will clarify things. It’s only with the powder that it says “maximum 50°C”; there, the higher temperature speeds up the dissolution of the substances. Regards, Wolfgang

bernhardmangelsgmxde

I would never have thought of using warm water. It works perfectly well even with water at room temperature. (At least for my modest standards...)

SxDx

Sorry for the late reply, I was having trouble with my account, but the boss sorted it out, thanks again! :rolleyes: I was also wondering why you’re supposed to mix a liquid concentrate with warm water. I’ll quote from the technical data for Agfa SW chemicals – paper processing from 2004:

Neutol, Neutol Liquid NE, Neutol Liquid WA ... Preparation instructions The developer concentrate is diluted with water at approx. 30 °C to the desired final volume and mixed thoroughly. The developer is ready for use once it has cooled to working temperature.

I then carried out a small experiment, preparing batches using water at temperatures of 20°C and 30°C respectively. It was clear that, when viewed in a glass bottle, the mixture with the ‘cold’ water still showed streaks in the first few minutes, as if the water and developer had not yet mixed completely. The next time I checked after 15 minutes, both were equally well mixed, with no streaks visible. I also noticed that both batches had cooled down slightly shortly after mixing – perhaps a chemical reaction? In any case, the 20°C solution was only 18–19°C immediately after mixing (as accurately as I can measure it with my simple thermometer). It can’t really have been down to room temperature, as that was actually above 20°C and the surface area exposed to evaporation in the bottle was also small. These two points seem to be the reason why Agfa recommends using warm water to be on the safe side. In future, however, I’ll just use room-temperature water. By the time the first sheet of paper goes into the tray, the mixture will have been ready for a while and the temperature will be back to normal. Regards Matthias

Xenar

Hello Matthias, You’ve observed that very well! The effect is not chemical, but purely physical. It is known as the enthalpy of solution, or more specifically in this case, the cooling effect of solution. Mixing the two liquids requires a certain amount of energy, which is removed from the system. The so-called internal energy decreases and manifests itself externally as a drop in temperature. If you prepare the solution with water at 22–23°C, you can work with it straight away. The opposite occurs when, for example, you carry out dilution of sulphuric acid with water (that’s right, everyone still remembers: ‘water first, then the acid, otherwise disaster strikes!’). By altering the internal structure, a huge amount of heat of solution is released here; the temperature of the mixture is higher than that of the original components. So much for the little digression into physical chemistry. And now off to the chemistry lab, to put theory into practice! Wishing you a lovely evening, Volker

Wolfgg

Forty years ago, Agfa added liquid concentrates to its existing powder versions, claiming they were "ready to use straight away". Trying to mix them at 30°C would be a joke. So: add water at just over 20°C, give it a quick stir until the streaks disappear, and you’re good to go. Regards, Wolfgang