chemistry technology

Hydrogen,  the  first  element  in  the  periodic  table,  is  a  very  widely  distributed  element.  Its  most important  compound  is  water,  H2O.  Hydrogen  is  found  in  most  of  substances,  which  constitute  living matter: sugar, starch, fats, and proteins. It occurs in petroleum, petrol, and other hydrocarbon mixtures. It
is also contained in all acids and alkalis. There are more compounds of hydrogen known than of any other
element.
Pure  hydrogen  is  a  colorless,  odorless,  tasteless  gas.  It  is  the  lightest  of  all  gases,  density  being about  1/14  that  of  air,  viz.  0.08987  gm.per  liter.  It  does  not  support  respiration,  but  is  not  poisonous. Hydrogen is a good conductor of heat as compared with other gases. Its specific heat is also higher than most other gases.
Hydrogen  is  a  combustible  gas,  burning  in  air  or  oxygen  with  a  nearly  colorless  flame  to  form water  vapor.  Hydrogen  also  readily  combines  with  fluorine  and  chlorine,  less  readily  with  bromine, iodine, sulfur, phosphorus, nitrogen, and carbon.
The element is made commercially by the electrolysis of water, and is used in large quantities in
the manufacture of ammonia, in the hydrogenation of liquid fats to form solid fats, and in the production
of high temperatures.
In the laboratory hydrogen may be easily prepared by the reaction of an a
cid as sulfuric acid, with a metal such as zinc:
H2SO4  + Zn = H2  + ZnSO4
Hydrogen may be set free also by the action of certain metals on water. Thus sodium and potassium react  with  cold  water,  producing  sodium  hydroxide  and  hydrogen.  Boiling  water  may  be  readily decomposed  by  ordinary  magnesium  powder,  while  steam  is  decomposed  by  heated  magnesium,  zinc, iron, cobalt, lead, tin, and nickel, but not by silver or copper.
Hydrogen is evolved by the action of zinc, magnesium and iron on dilute hydrochloric and sulfuric acid on aluminum and tin.
A solution of caustic soda or potash readily dissolves zinc or aluminum on warming, with evolution
of hydrogen and formation of a soluble zincate or aluminate.