"Cold hydrochloric acid" is simply hydrochloric acid (HCl) at a temperature below room temperature. It's not a specific chemical compound, but rather a description of its physical state.

Here's why it's important to mention the temperature:

* Reactivity: HCl is a very reactive acid. Its reactivity can change depending on its temperature. Generally, colder HCl will react slower than warmer HCl.

* Safety: Cold HCl is generally safer to handle than warm HCl, as its corrosive properties are reduced at lower temperatures. However, all concentrations of HCl should be handled with care and appropriate safety precautions.

Important Note: You should always check the specific context of where you encounter the term "cold hydrochloric acid". It might be referring to a specific temperature range or a specific application.