(Chemical symbol: H). Hydrogen is a chemical element that occurs in free state in the gases of certain volcanoes. In combination with other elements it is found in most organic compounds and many inorganic compounds. Water is a chemical compound of hydrogen and oxygen, in which approximately 11% by weight is hydrogen.
Hydrogen is the lightest element known; it has an atomic weight of 1.008, compared with 16 for oxygen. The density as compared with air is .0695. In gas form, hydrogen is colorless, odorless, and tasteless.
When liquefied, it is a clear and colorless liquid. Under atmospheric pressure the boiling point of hydrogen is -252.5”C (-422.5”F).
Hydrogen combines readily with oxygen in the presence of heat, and forms water. Hydrogen and oxygen bum together with an almost colorless flame.
They produce a very hot flame that can be utilized for various purposes, such as lead burning, brazing, and for welding aluminum. The principal objection to the oxyhydrogen flame is that it is very difficult to determine whether the flame is neutral or not, because of the absence of a definite inner cone in the flame.
Hydrogen can be manufactured either by steam reformation of hydrocarbons, partial oxidation of coal or hydrocarbons, or electrolysis of water. The most widely used commercial method is steam reformation of natural gas or an alternate feedstock such as propane or refinery gases. In this process the hydrocarbon source is reacted with superheated steam in the presence of a nickel catalyst to produce hydrogen plus some other gaseous by-products. The gas stream is then passed through an absorption bed to purify the product and produce pure hydrogen.
Where steam reformation is uneconomical, hydrogen is manufactured by partial oxidation of hydrocarbons. With this method combustion takes place in special burners that oxidize the input material in an oxygen deficient atmosphere in the presence of water vapor. Purification is accomplished in a manner similar to that used in steam reformation.
Hydrogen is supplied to users in seamless, drawn steel cylinders, charged to a pressure of 13.8 MPa at 21°C (2000 psi at 70°F).The size of the hydrogen cylinder standardized by the gas industry has a capacity of about 5.4 m3 (191 cu. ft).