Sciencemadness Discussion Board

Vapour temperature of a boiling salt solution

Prepic - 3-9-2020 at 08:54

Hey all,

I've been busy trying to distill down a solution of nickel (II) chloride and I set my heating mantle to roughly 190°C in order to get a good, consistent drip rate of water.

So my question is this; I understand that the salt solution will boil at a higher temperature but what is the temperature of the water coming over? Should the water boiling off be at 100°C (saturated) or at the boiling temperature of the salt solution (i.e. superheated)?

I personally never thought of this too much but now that I have, I don't really know. Any comments would help. Thanks in advanced!

Maurice VD 37 - 3-9-2020 at 09:29

There is no general rule. Some hydrates are loosing water at 110°C, some at 120°C, some at higher temperatures. The temperature where the water will be eliminated is empirical. You cannot calculate it from a priori data.

Prepic - 3-9-2020 at 09:42

Quote: Originally posted by Maurice VD 37  
There is no general rule. Some hydrates are loosing water at 110°C, some at 120°C, some at higher temperatures. The temperature where the water will be eliminated is empirical. You cannot calculate it from a priori data.


Thanks for your response Maurice VD 37; I hope to clarify that my nickel (II) chloride solution still contains excess water and I am not heating the hydrated salt directly.

Tsjerk - 3-9-2020 at 12:03

The water vapour leaving the solution will have the same temperature as the solution, which makes sense as it will not suddenly cool down to 100 degrees when it leaves the solution.