The liquid is sodium acetate, sodium acetate, in simple terms. Getting it at home is a piece of cake. Take baking soda and vinegar, or even better - vinegar essence - you will have to evaporate less. Connect them gradually until an approximately neutral reaction, that is, until the hissing stops. There is no need for special precision or purity here. Evaporate, cool, you get a monolithic piece. There may still be some solution left on top; if it hasn’t been evaporated enough, pour it away. What remains is sodium acetate, or rather, its crystalline hydrate. The rest is simple. Put it on the fire, your piece melts. Carefully pour the clear melt into another bowl to get rid of sediment and debris at the bottom. Pour the clean melt hot into a transparent glass, cover with a dust cloth so that it does not accidentally freeze ahead of time, and cool to room temperature. Liquid - liquid. But as soon as you drop a tiny grain of the same sodium acetate there (you can get it from what’s left after draining), the liquid will harden before your eyes! The composition can be used repeatedly! Good luck!