They consist of liquid hydrofluoric acid (HF). It melts at тИТ83┬░тАКC and boils at 19.4┬░тАКC. In it are dissolved varying quantities of metallic and nonmetallic fluorides, such as boron trifluoride, sodium fluoride, etc. When the oceans and lakes freeze, they do so from the bottom up, so there is no layer of ice over free liquid. + 