Changes

=== Glass Industry ===

=== Glass Industry ===

Main article Glass (काचः)

{{Main article|Glass (काचः)}}

Generally, glass is produced by melting a mixture of silica (sand: about 75%), soda (about 15%) and calcium compound (lime: about 10%) with the desired metallic oxides that serve as coloring agents.<ref>Story of Glass in India & the World by Pankaj Goyal</ref> Origin of glass is shrouded in mystery and scholars note that it is difficult to pinpoint the exact period. Modern archeological evidence proved that Mesapotamia, Egypt and India made various siliceous and glazed materials including faience (glazed siliceous ware), glazed pottery and glass.<ref name=":8" />

Generally, glass is produced by melting a mixture of silica (sand: about 75%), soda (about 15%) and calcium compound (lime: about 10%) with the desired metallic oxides that serve as coloring agents.<ref>Story of Glass in India & the World by Pankaj Goyal</ref> Origin of glass is shrouded in mystery and scholars note that it is difficult to pinpoint the exact period. Modern archeological evidence proved that Mesapotamia, Egypt and India made various siliceous and glazed materials including faience (glazed siliceous ware), glazed pottery and glass.<ref name=":8" />

== Chemistry in Minerals and Metals ==

== Chemistry in Minerals and Metals ==

Many processes involved in extraction of metals from ores to their purification deal with advanced knowledge of chemistry. Many ancient and medieval texts reveal that people had this knowledge as outlined below.<ref name=":2" /><ref name=":4" />

Many processes involved in extraction of metals from ores to their purification deal with advanced knowledge of chemistry. Many ancient and medieval texts reveal that people had this knowledge as outlined below.<ref name=":2" /><ref name=":4" />