Laboratory works require apparatus
made in a Borosilicate 3.3 expansion glass which offers maximum
inertness to widest range of
chemical substances, withstand thermal shock, high temperature without
deforming and resilient enough to
withstand the normal laboratory handling, washing and sterilizing
processes.
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Borosilicate glass represents
unmatched standardized glass for construction of Laboratory
Glasswares. Its steadly growing
use is due to many advantages over conventional materials.
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Borosilicate glass is chosen for
its unique chemical and physical properties. Borosilicate glass can be
considered as being composed of
oxides. Silica (SiO2 ), boric oxide (B2O3 ) and phosphorous
pentaoxide (P2O5 ) are chief
glass form oxides. Soda (Na2O), Lime ( CaO ), Alumina (Al2O3 ) Potash
(K2O) Magnesia (MgO) and lead
oxide (PbO) are the principle modifiers/fluxes.
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CHEMICAL COMPOSITION
The composition of borosilicate
glass used has following approximate composition.
SiO2 - 80.6
%B2 O3 - 12.5%
Na2O - 4.5 %Al2 O3 - 2.2
%
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RESISTANCE
TO CHEMICALS
Borosilicate glass is inert to
almost all materials except hydrofluoric acid (HF) phosphoric acid (H3PO4)
and hot strong caustic solutions.
Of these, Hydrofluoric acid has the most serious effect, even when it is
present in PPM (parts per million)
in solutions, Whereas phosphoric acid and caustic solutions cause
no problems when cold but at
elevated temperature corrosion occurs. In case of caustic solutions upto
30% concentration can be handled
safely at ambient temperature.
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Under actual operating conditions,
the effect of turbulance, and traces of other chemicals in the
solution may increase or decrease
the rate of attack. So it is not possible to give exact figures for
corrosion by caustic solutions.
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THERMAL
PROPERTIES
Linear coefficient of thermal
expansion the coefficient of thermal expansion of borosilicate glass over
the temperature 0-300 OC is
33 x 10-7 / OC. This is very low when compared with other glasses
and
metals. That is why borosilicate
glass is often called low expansion borosilicate glass.
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SPECIFIC HEAT
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Specific heat between 25OC and 300
C is average to be 0.233Kcal/Kg C.
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THERMAL CONDUCTIVITY
Thermal conductivity is 1.0
Kcal/hr. m C over the permissible operating temperature range.
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ANNEALING
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Annealing of glass is the process
where the glass is heated and kept for a defined period of time to relieve
internal stresses. Careful cooling under controlled conditions is essential
to ensure that no stresses are reintroduced by chilling/cooling.
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MECHANICAL
PROPERTIES
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The lack of ductility of glass
prevents the equalization of stresses at local irregularities or flaws and
the
breakage strength varies
considerably about a mean value. This latter is found to occur at a tensile
strength of about 700kgs/cm.
In order to allow for the spread
of breaking stress, a large factor of safety is applied when determining the
wall thickness requirement to
allow operation up to specified limit of working pressure.
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OPTICAL
PROPERTIES
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Borosilicate glass shows no
appreciable absorption in the visible region of spectrum and therefore
appears clear and colorless. In photo chemical process the transparency of
ultra violet is of particular importance. It follows from the transmittance
of material in UV region that photochemical reactions such as chlorination
& sulpho -chlorination can be performed in it.
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Head
Office :
C-31/A, Sardar Estate, Ajwa Road,
Vadodara - 390 019 Gujarat, India
Ph. : +91-265-2561595, 2521181 l
Fax : +91-265-2561482, 2511428
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