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nw NC | I'm small time operator and we always got the amounts of fertilizer that we needed in 50 lb bags on pallets. Some years ago I had a few bags of old ammonium nitrate that had solidified. I put about 35 gallons of water in a plastic 55 gallon barrel and started adding the AN to it and stirring. It did dissolve . Odd thing happened during the dissolving process though, the water started getting cold. It was about 60 F temp that day. Dew started forming on the outside of the barrel. It was not very long until frost formed all over the outside surface of the barrel. The water and nitrogen solution was VERY cold to the touch. I got a thermometer and put it into the solution. It was well below freezing temp at that point and it kept getting colder. Finally got to 10 degrees F. Solution remained liquid the entire time.
I used the solution as a liquid form of nitrogen, probably on some grassland.
I searched this : Why does dry nitrogen fertilizer make the water it dissolves in get cold?
And found this: It gets cold because the process of dissolving some dry nitrogen fertilizers like urea and ammonium nitrate in water is an endothermic reaction. This means that the dissolving process requires more energy to break the bonds within the fertilizer molecules and separate them in the water than the energy released when the dissolved ions or molecules interact with the water molecules. In other words, to break down the fertilizer's structure and spread out in the water, it absorbs heat from its surroundings, including the water itself. This absorption of heat causes the temperature of the water to decrease, making it feel cold. This phenomenon is also why ammonium nitrate is used in instant cold packs.
Edited by WJKEIGER 8/14/2025 15:35
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Melting urea
