SCHOTT Technical Glasses

11
Surface test method B
(at 121 °C, according to ISO 4802-2 (2010) and current
Ph. Eur.)
Grain-titration methods are always carried out on crushed
glass samples and the glass is tested as a material. With the
surface test method, in contrast, the water resistance of
the surface can be determined in its “as delivered” state. In
this method, new, undamaged vessels (e.g. flasks, test
tubes, vials, ampoules) are filled with water and heated for
60 min at 121 °C in an autoclave. The leaching solution is
then analyzed by using flame atomic emission or adsorption
spectrometry (flame spectrometry). This is a direct and
precise method for quantifying the specific leached ions in
the solution. Distinguished according to volume, the containers
are classified according to the mean value of the
concentration of the oxides.
2.2.2 Acid resistance, according to DIN 12116
The glass surface to be tested is boiled for 6 h in 20 %
hydrochloric acid [c(HCI) = 6 mol/l], and the loss in weight
is determined in mg/100 cm 2 . Using the half loss in weight,
the glasses are then classified as follows:
Alkali class
Designation
Loss in weight
after 3 h
mg/100 cm 2
1 low alkali attack up to 75
2 slight alkali attack above 75 up to 175
3 high alkali attack above 175
Table 4. Alkali classes
Alkali classes for glasses manufactured by SCHOTT are
listed in Table 20, p. 68ff.
The following borosilicate glasses have particularly
high chemical resistance: DURAN ® /BOROFLOAT ® 33/
SUPREMAX ® (8330), SUPRAX ® (8488), FIOLAX ® clear
(8412), FIOLAX ® amber (8414) and PYRAN ® S (8341);
see Table 6, p. 30.
2
Acid class
Designation
Half loss in weight
after 6 h
mg/100 cm 2
1 highly acid resistant up to 0.7
2 acid resistant above 0.7 up to 1.5
3 slight acid attack above 1.5 up to 15
4 high acid attack above 15
Table 3. Acid classes
Acid classes for glasses manufactured by SCHOTT are listed
in Table 20, p. 68ff.
2.2.3 Alkali resistance, according to DIN ISO 695
To determine the alkali resistance, glass surfaces are subjected
to a 3 h treatment in boiling aqueous solution consisting
of equal volumes of sodium hydroxide, c(NaOH) =
1 mol/l and sodium carbonate, c(Na 2 CO 3 ) = 0.5 mol/l. The
loss in weight is then determined, and the glasses are classified
as follows:
FIOLAX ® highly chemical resistant glass for save primary packaging
in the pharmaceutical industry