A serious problem in the use of nitroglycerin results from its high freezing point of . Solid nitroglycerin is much more sensitive to shock than the liquid, a common feature in explosives. In the past, nitroglycerin was often shipped in the frozen state, but this resulted in a high number of accidents during the thawing process just before its use. This disadvantage is overcome by using mixtures of nitroglycerin with other polynitrates. For example, a mixture of nitroglycerin and ethylene glycol dinitrate freezes at .