Tetanus vaccine can help prevent tetanus disease, commonly known as lockjaw.. Tetanus is a serious disease that causes painful tightening of the muscles, usually all over the body. It can lead to locking of the jaw so the person cannot open his mouth or swallow. Tetanus leads to death in about one in ten cases.
The most abundant dissolved salt in ocean water is sodium chloride. It is a colorless crystalline compound with the chemical formula of NaCl.
In fresh water the concentration of salts, or salinity, is nearly zero. The salinity of water in the ocean averages about 35 parts per thousand (ppt). The mixture of seawater and fresh water in estuaries is called brackish water and its salinity can range from 0.5 to 35 ppt.