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Making a waffle out of sodium acetate trihydrate. This is the same stuff that makes up “hot ice” and heating pads.

How is the liquid made?

I used vinegar and baking soda to make the liquid. Boiled off the water to leave a super saturated salt solution. The salt is normally a solid at room temperature, so when it cools off in the waffle iron, it solidifies.

Vinegar contains the acetic acid.
Baking soda is sodium bicarbonate.
Sodium acetate is the salt formed.

The chemical reaction

acetic acid + sodium bicarbonate —-> sodium acetate + carbonic acid

HC₂H₃O₂ + NaHCO₃ —-> NaC₂H₃O₂ + H₂CO₃

The carbonic acid breaks down almost immediately into water and CO₂.

H₂CO₃ —-> H₂O + CO₂

The CO₂ bubbles out of the liquid, leaving just sodium acetate dissolved in water. The sodium acetate binds 3 water molecules to create sodium acetate trihydrate:

NaC₂H₃O₂ + 3 H₂O —-> C₂H₉NaO₅

The sodium acetate trihydrate is what is shown in the videos on this page.

Here is a video that shows how the liquid is made.

Sodium Acetate Trihydrate is a solid at room temp. It melts at 58C (136F). Boils at 122C (252F).

Molding with Salt Crystals

There could be some molding potential for this material. I wonder what interesting creations could be made by pouring this liquid into a mold, as is done with concrete? Care would have to be taken with a mold out of this material, because water would make it dissolve and disassemble. That could be an advantage, however, if you want a temporary mold.

One idea:   make a rain switch.   Place a spring-loaded switch inside a mold of this salt and place the mold outside. When it rains, the salt dissolves, allowing the switch to close. Then, a circuit of your choice could be enabled. So when it rains, your switch would turn on (or off if you wire it that way).