Chemical Composition
The following table shows a typical analysis of Borosilicate Glass 3.3
Element	Weight %
Silica (SiO2)	80,60
Boric oxide (B2O3)	12,60
Sodium oxide (Na2O3)	4,20
Aluminia (Al2O3)	2,20
Iron oxide (Fe2O3)	0,04
Calcium (CaO)	0,10
Magnesium oxide (MgO)	0,05
Chlorine (Cl)	0,10
There may be heavy metals in a concentration of less than five parts per million.

Borosilicate glass 3.3 is specified as a standard glass - it contains mainly sand, calcium carbonate and sodium carbonate. High quality sand, dehydrated borate boric acid, alumina and salt are used in its manufacture and strict control is applied to ensure the specifications for purity and consistency of these materials are maintained.