 |
| LOW
EXPANSION BOROSILICATE GLASS |
| From the 16th Century to today, chemical research teams
have used glass containers for a very basic reason the
glass containers is transparent, almost invisible. And
so the contents and the reaction are clear visible, But
because chemists music heat, cool and mix chemical substances,
ordinary glass is not always adequate or laboratory works. |
| |
| Laboratory works requires apparatus made in a glass
- which can readily be mould ed into any desired shape
or from which offers maximum inertness when in contact
with the widest range of chemical substances, which can
withstand thermal shock with fracture and high temperature
work without deforming, and which will be resilient enough
to survive the everyday knocks to which it will be subjected
in normal laboratory handling, washing and sterilizing
processes. |
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| Chemical
Composition |
| Glassco Glassware is a low alkali borosilicate composition.
Its typical chemical composition is given under. It is
virtually free of magnesia-lime-Zinc group and contains
only traces of heavy metals. |
| |
Percentage
by weigh |
| SiO2 |
81 |
| B2O3 |
13 |
| Na2O |
4 |
|
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| In general the 'Strain point' should be regarded as
the maximum safe operating temperature of Glassco glassware.
When heated above 500° C the glass may acquire permanent
stresses on cooling. All Glassco lab ware is annealed
in modern ovens under strictly controlled conditions to
ensure minimal residual stress in the products. |
| |
| Chemical
Durability |
| Glassco Glassware in highly resistance water, neutral
and acid solutions, concentrated acids and their mixtures
as well as to chloride, bromine, iodine, and organic matters.
Even during extended period of reaction and at temperatures
above 100° C, its chemical resistance exceeds tha
of mot metals and other materials. It can withstand repeated
dry and wet sterilisation without surface deterioration
and subsequent contamination. Resistance to attack of
various chemicals is shown under. Only hydroflioric acid,
very hot phosphoric acid and alkaline solutions increasinglly
attack the glass surface with rising concentration and
temperature. |
| |
Contact
Chemical |
Duration
in hour |
Loss
in Wt. mg/m |
| Water distilled at 100°C |
6 |
10 |
| Water Vapour Steam at
121°C |
1 |
75 |
| Acid HCI |
6 |
100 |
| 80% H2So4at 130°C |
12 |
140 |
| Alkali - 1N soln. of NA2Co3
boiling Infusion Fluids Isotonic |
6 |
4000 |
| Nacl(0.85%) 121°C |
2.5 |
70 |
| Glucose(5%)121°C |
2.5 |
50 |
|
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| Fabrication
with Borosilicate Glass |
| Due to low expansion of glass and easy workability,
this glass can be shaped, formed, joined into complicated
apparatus. It can be done even by an analyst in his own
laboratory. He can keep on changing till he gets what
he needs. In case where annealing in a controlled oven
is difficult he can do so b flame annealing which is also
great advantage. |
| |
| Optical
Properties |
| Laboratory glassware made form Borosilicate Glass shows
no noticeable absorption in the visible region of the
spectrum. It appear consequently clear and colourless. |
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