Salt is a key part of our diets. It's also vital for our survival, as dietitian Lena Beal, MS, RDN, LD and National Spokesperson for the Academy of Nutrition and Dietetics previously told USA TODAY.

Cold packs are presumably ammonium salts (judging by the stated contents). The temperature change is apparently the heat of solution of the salt.

Digitalis, a low-salt diet, ammonium chloride and semiweekly injections of mercurial diuretics had failed to prevent the accumulation of edema. Physical examination revealed a thin, markedly ...