View Full Version : Mixing salt made temperature spike

09/14/2010, 04:10 AM
Searching the forum last hours but could not find a explanation for this issue, I know is already posted but can not find explanation.
What create temperature spike when salt is mixing in a can/container?
Artifical salts is aded to can with ro water, smal quantity of salts to avoid precipitation, freshly mixed sea water become hotter and hooter, up to 2-3 degree celzius.

09/14/2010, 04:28 AM
I'm too keen on chemical reaction explanation that cause the temperature spike when mixing salt.

09/14/2010, 09:25 AM
So of the salts give of what we call a exothermic reaction Blue. When you add powdered kalk, Ca(OH)2, to water for example the water will warm up.

Exothermic Reaction vs Endothermic vs Balanced

When a bond is broken, such as that between the Ca++ and (OH)2 or certain other substance that go into solution heat is given off. So, if the energy released by the bond breaking is greater than the energy consumed by the bond breaking heat is given off ( like a heat pack). Now, if the consumed energy by the bond breaking is greater that the energy released by the bond braking the reaction is Endothermic and the temp drops ( like a cold pack). If both energy's are the same then the temp stays the same.

09/14/2010, 10:36 AM
Thank you for explanation Boomer, very apreciated.

Is that reaction sign of bad salt or bad ingredients or is not important at all and salt is quite fine regarding exotermic reaction? So far exotermic reaction is only reported localy with one salt brand, probably not to much known in USA, salt brand is Wave Optimum Pro Reef Salt here is the only info what I can find about that salt, is second item on salt study http://www.tanktests.co.uk/index.php?target=pages&page_id=salt_water_study

09/14/2010, 12:12 PM
Not sure why it is doing that but it may be due to the fact it is really low in major ions. It is like the worst salt on that test. It is very low in Mg++ like 325 ppm and if this was more like 1200 or 1300 pm that may cancel out the heat and the Exo -reaction.

In regards to the ref solutions for testing. Somebody is off here and I do not know if it Salifert or Fauna Marine. Claude tells me his are double checked but Simon tell me his are off as are his other ref. So, I do not know who to believe.

From the tester

I also found an issue with the salinity of the FM reference solution. It is supposed to read 35ppt, but I calibrated my refractometer with zero TDS RO water, checked it several times, and the salinity of the reference solution read 34ppt.

He is kind of lost here :) You can not calibrate a refract in RO/DI and get it accurate. If it is a lab grad refract it will always read 1.5 ppt to low if you read it as 35 ppt. It is SUPPOSE to, as it is a NaCl refract and not a seawater refract. Meaning, if you are making up a salt mix, using a refract like he is using, it needs to read 36.5 to equal 35 ppt seawater, when cal in RO/DI water. And if you cal in RO/DI and put a 35 ppt ref on it, it should read 36.5 ppt. And if you made up a salt mix till the meter reads 35 ppt it is really 33.5 ppt.

With that said, the FM ref

35 ppt ref + 1.5 ppt = 36.5 ppt, what it should have read. The accuracy of refracts are +/- 1 ppt so it falls right in-line i.e, 35.5 ppt - 37.5 ppt. So, does this mean the FM ref is off ??? NO, as many of these cheap Chinese refracts are way off to begin with and some as much as 4 ppt when cal in RO/DI water and some are off zero. A Lab grade refract will always have an off-set of 1.5 ppt in RO/DI for seawater.

With that ref the refract should be re-calibrated to read 35 ppt with that 35 ppt ref solution. This will make it accurate for a narrow range of Salinity of ~ 31 - 40 ppt. If you go beyond this the optics of the glass will skew this more.

The new D-D refract, the Vee-Gee/ Vital Sine are all Seawater refracts and NOT Table Salt refracts like all the rest of them, par maybe the new Atago, which is suppose to be for seawater @ $250 USA

Your tester is not saying who's refract he is using.

As as this UK company goes I will challenge any of their tests just like we did for AWT test. Here is a link mas to what then say they can test


I see nothing on testing procedures and/or accepted seawater test methods or if they even know seawater testing is not the same as FW testing. It is very odd that they gave that salt assay test and used test kits :) They seem to be very confused IMHO, i.e, lost on refracts, testing with test kits for this study, using aquarium company ref stds = lost :D

09/14/2010, 03:13 PM
I agree that RO/DI water isn't appropriate for calibrating a refractometer to read saltwater. This article has some information on the subject:


09/14/2010, 10:03 PM
Can't help with the thread but... I count on the cool RODI water warming as the salt and water mix. However I always attributed the warming to the submersible pump and friction. I don't think I've ever seen more than about 4-5 F over room temp though.