Question

what do you mean by solid ice and co2 is kept in low pressure

Answer 1

dry ice or soid ice is basically  solid co2.when co2 in kept for some time under high pressure and low temp it turns into solid ice

Answer 2

Solid ice is also known as dry ice in which carbon dioxide solidifies into ice cubes. \mathrm{co}_{2} is kept under low pressure so that the solid state of dry ice can be maintained. If the pressure is increased, the solid carbon dioxide again starts vaporizing into its gaseous state.