Physical and Chemical Properties
Linear expansion coefficient (@ 20/300 0C) 3.3•10-6 K-1
Strain point 520 0C
Annealing point 560 ± 10 0C
Softening point 820 ± 10 0C
Density 2.23 ± 0.02 g/cm3
Hydrolytic resistance (according to ISO 719, water at 98 0C) Class 1
Hydrolytic resistance (according to ISO 720, water at 121 0C) Class 1
Resistance to acids (according to ISO 1776, DIN 12116) Class 1
Resistance to alkalis (according to ISO 695) Class 2
Typical Composition
80,4% in weight SiO2
13,0% in weight B2O3
4,2% in weight Na2O
2,4% in weight Al2O3
PROPERTIES OF OUR BOROSILICATE GLASSWARE
Hydrolytic resistance
1. The resistance is determined with two methods, at 98 0C and at 121 0C: 1. Acc. to DIN ISO 719
corresponds to hydrolytic resistance class 1 (of five classes). The amount of Na2O/g glass grain leached out after
one hour in water at 98 0C is measured. The quantity of Na2O leached out is less than 3 μg/g of glass grain.
2. It also corresponds to hydrolytic resistance class 1 acc. to DIN ISO 720 (of three classes). The quantity of
Na2O leached out after one hour in water at 121 0C is less than 62 μg/g of glass grain. Due to its good
hydrolytic resistance meets the requirements of the USP, JP and EP for a neutral glass according
to glass type 1. Therefore it can be used in an almost unrestricted way in pharmaceutical applications and in
contact with foodstuffs.
Acid Resistance
Acid resistance can be determined by two methods:
1. In accordance with DIN ISO 12116 - corresponds to class 1 (of four classes). The acid removal
is measured at fire finished glass surfaces, as a time dependent weight loss under the exposure of 18 %
hydrochloric acid. After a boiling period of three hours this removal is only 0,3 mg/dm2.
2. In accordance with DIN ISO 1776 the attacked layer thickness of the glass is examined in dependency
of the type of acid and its concentration. The maximum attack occurs at acid ranges of 4-7 n. At higher
concentrations, the reaction rate decreases significantly, so that the layer thicknesses which are attacked are only in the range of a few thousand μm after years. Thus, the mechanisms of acid attack are not relevant for the wall thicknesses of laboratory glasses used in practice.
Alkali Resistance
In accordance with DIN ISO 695 corresponds to alkali resistance .The surface erosion after three hours boiling in a mixture of equal volume fractions of sodium hydroxide solution (concentration 1 mol/l) and sodium carbonate solution (concentration 0,5 mol/l) is only 134 mg/100 cm2. The surface removal through alkali is directly proportional to time. A visible attack on the glass surface takes place only at temperatures above 600C, at lower temperatures the reaction rates are so low that hardly any reduction of the wall thickness takes place over a period of years. Long-term tests have shown that the use of NaOH with a concentration of 1 mol/l at an operating temperature of 500C produces a glass surface removal of 1 mm after 25 years in a continuous flow.
Autoclaving of Laboratory Glass
According to DIN 58900, part 1 and DIN 58946, part 1/2, 1987, hot air sterilization is the “killing resp. irreversible disabling of all augmentable microorganisms“ under the influence of “saturated steam of at least 1200C and 2 bar“. As minimum residence time (time to kill + excess time) is considered for 20 minutes at 1210C. A raised vapor temperature of 1210C is only possible with a raised pressure of 2 bars. Vessels must only be hot air sterilized with open closures, to avoid additional pressure build-up resulting in breakage.
Temperature Resistance When Heated And Thermal Shock Resistance
The maximum permissible operating temperature is 5900C. Above a temperature of 6260C begins to soften and at 8600C it changes to the liquid state. As it has a very low coefficient of linear expansion (a = 3.3 x 10-6K-1), a feature is its high thermal shock resistance (up to DT = 100 K). For a temperature change of 1 K, the glass hanges by only 3.3 x 10-6 relative lenght units, resulting in low levels of mechanical strain where a thermal gradient exists. The thermal shock resistance is depending on the wall thickness and geometry of the products.
Temperature resistance at low temperatures
can be cooled down to the maximum possible negative temperature and is therefore suitable for use with liquid nitrogen (approx. -1960C). During such freezing you have to observe the expansion of the content. In general products are recommended for use down to -700C. Besides the geometry of the products you also have to pay attention to the property of the used components. During cooling and thawing ensure that the temperature difference does not exceed 100 K. In practice, stepwise cooling and heating are recommended
Care & Maintenance of Laboratory Glassware
To obtain the maximum performance from your laboratory glassware correct handling is essential. The following information is a guide on the safe handling of Biohall glassware and tips on how you can optimize its performance and life span
General Precautions
We recommend that all glassware is washed before it is first used.
Before using any piece of glassware, always take time to examine it carefully and ensure that it is in good condition. Do not use any glassware that is scratched, chipped, cracked or etched. Defects like these can seriously weaken the mechanical strength of the glass and cause it to break in use.
Dispose of broken or defective glassware safely. Use a purpose-designed disposal bin that is puncture resistant and clearly labelled. glassware (or any other borosilicate glass) should under no circumstances be disposed of in a domestic glass recycling stream (e.g. bottle banks), as its high melting point makes it incompatible with other glass (soda-lime glass) for recycling. The correct method of disposal is to include it in the general waste in accordance with the relevant guidelines, provided that the glass is free from any harmful chemical contamination.
Never use excessive force to fit rubber bungs into the neck of a piece of glassware. Always ensure that you select the correct size of bung.
Many glass products are supplied with durable, easy to use plastic screw thread tubing connectors to allow the safe fitting of any flexible tubing. When attaching tubing, ensure that the screw thread connector is removed from the glassware, the tubing is lubricated and protective gloves are worn. Never use excessive force to connect the rubber hose or tubing.
Carrying or lifting large glass flasks, beakers or bottles, etc. by the neck or rim can be very dangerous. Always provide support from the base and sides.
When stirring solutions in glass vessels, avoid using stirring rods with sharp ends which can scratch the glassware causing it to become weakened.
Heating and Cooling
The maximum recommended working temperature for glassware is 500 OC (for short periods only). However, once the temperature exceeds 150 OC extra care must be taken to ensure that the heating and then cooling of the glassware is achieved in a slow and uniform manner.
Always heat glassware gently and gradually to avoid sudden temperature changes which may cause the glass to break due to thermal shock. Similarly, allow hot glassware to cool gradually and in a location away from cold draughts.
If you are using a hotplate, ensure that the top plate is larger than the base of the vessel to be heated. If the base of the vessel overhangs the hotplate top, hotspots can occur causing the base of the vessel to break. Also, never put cold glassware onto a pre-heated hotplate. Always warm up the glassware from ambient temperature.
If you are using a Bunsen burner, employ a soft flame and use a wire gauze with a ceramic centre to diffuse the flame. Never apply direct localised heat to a piece of glassware.
borosilicate glass is microwave safe. However, as with any microwave vessel, ensure that it holds microwave absorbing material, before placing it in the oven. Many of our products utilise plastics screwcaps and connectors. These components are typically manufactured from polypropylene or PTFE, both of which are also microwave safe.
When autoclaving containers e.g. bottles with screwcaps, always loosen off the caps. Autoclaving glassware with a tightly screwed cap can result in pressure differences which will cause the container to break.
Vacuum and Pressure Use
Because working conditions can vary enormously, Biohall cannot guarantee the performance of any of its glassware when used under vacuum or positive pressure. The application of positive pressures inside glass
apparatus is particularly hazardous and should be avoided, if at all possible. Safety precautions should always be taken to protect personnel and a number of these are listed below:
Always use an adequate safety screen and/or protective cage when using glassware under vacuum or positive pressure.
Flat bottomed vessels such as Erlenmeyer flasks and bottles should not be used under vacuum as they are likely to implode. Exceptions are vessels with specially thickened walls such as Buchner filter flasks and desiccators.
Under no circumstances should glassware that is scratched, cracked or chipped be used. Any damage to the glassware will seriously impair its mechanical strength. Never subject glassware to sudden pressure changes. Always apply and release pressure gradients and vacuums gradually. Avoid stressing the glass by over-tightening clamps. Support glassware gently where possible
