Glass Types & Properties
Glass Standards
The glass products supplied by DWK Life Sciences are manufactured from different glass types which comply with the following international standards:
| Standard | 3.3 Expansion Borosilicate Glass | 4.9 Expansion Borosilicate Glass (Clear) | 5.4 Expansion Borosilicate Glass (Amber) | 7.8 Expansion Soda-Lime Glass (Amber) | 9.1 Expansion Soda-Lime Glass (Clear) |
|---|---|---|---|---|---|
| ASTM E-438 | Type 1 Class A | Type 1 Class B | Type 1 Class B | Type 2 | Type 2 |
| US Pharmacopoeia (USP) | Type 1 | Type 1 | Type 1 | Type 3 | Type 3 |
| European Pharmacopoeia (EP) | Type 1 | Type 1 | Type 1 | Type 3 | Type 3 |
3.3 Expansion borosilicate glass also complies with ISO 3585 and DIN 12217.
Due to the demanding conditions that laboratory glassware is subjected to, maximum chemical toughness, minimum thermal expansion and high resistance to thermal shock are the key properties of 3.3 expansion borosilicate glass that make it the ideal material for use in the laboratory.
Many DWK Life Sciences products conform to other standards set out for laboratory glassware; for example glass beakers comply to ISO 3819 and volumetric flasks comply to ISO 1042 and DIN 12664. Typically these standards will specify not only glass type, but also dimensional detail, volumetric accuracy and tolerances.
Chemical Composition
3.3 Expansion borosilicate glass has a very high resistance to attack from water, acids, salt solutions, halogens and organic solvents. Only hydrofluoric acid, hot concentrated phosphoric acid and strong alkaline solutions cause appreciable corrosion of the glass. Neutral borosilicate glass (ASTM E-438 Type 1B) also has excellent chemical resistance properties which make it ideal for the storing or packaging of acidic, neutral and alkaline products and for injectable solutions. Soda-lime glass (ASTM E-438 Type 2) is less chemically resistant than borosilicate glass and is typically suitable for storing dry powders and for containers for general sample storage applications.
Different glass types have the following typical chemical composition (approx. % by weight):
| Chemical | 3.3 Expansion Borosilicate Glass | 4.9 Expansion Borosilicate Glass (Clear) | 5.4 Expansion Borosilicate Glass (Amber) | 7.8 Expansion Soda-Lime Glass (Amber) | 9.1 Expansion Soda-Lime Glass (Clear) |
|---|---|---|---|---|---|
| SiO2 | 80.60% | 75.00% | 70.00% | 67.00% | 69.00% |
| B2O3 | 13.00% | 10.50% | 7.50% | 5.00% | 1.00% |
| Na2O | 4.00% | 5.00% | 6.50% | 12.00% | 13.00% |
| Al2O3 | 2.30% | 7.00% | 6.00% | 7.00% | 4.00% |
| CaO | - | 1.50% | <1.0% | 1.00% | 5.00% |
| Fe2O3 | - | - | 1.00% | 2.00% | - |
| Tio2 | - | - | 5.00% | - | - |
| K2O | - | - | 1.00% | 1.00% | 3.00% |
| BaO | - | - | 2.00% | <0.5% | 2.00% |
| Mno2 | - | - | - | 5.00% | - |
| MgO | - | - | - | - | 3.00% |
Please refer to the following table for more information on the physical and chemical properties of glass.
| 3.3 Expansion Borosilicate Glass | 4.9 Expansion Borosilicate Glass (Clear) | 5.4 Expansion Borosilicate Glass (Amber) | 7.8 Expansion Soda-Lime Glass (Amber) | 9.1 Expansion Soda-Lime Glass (Clear) | |
|---|---|---|---|---|---|
| Coefficient of Expansion (20-300° C) x10-6K-1 | 3.3 | 4.9 | 5.4 | 7.8 | 9.1 |
| Working Point ° C | 1252 | 1160 | 1165 | 1050 | 1040 |
| Softening Point° C | 821 | 785 | 770 | 720 | 720 |
| Annealing Point ° C | 565 | 565 | 560 | 540 | 530 |
| Transformation Temperature° C | 525 | 565 | 550 | 535 | 525 |
| Density at 25° Cg/cm-3 | 2.23 | 2.34 | 2.42 | 2.5 | 2.5 |
| Hydrolytic Resistance | |||||
| Acc. to ISO 719 | Class HGB 1 | Class HGB 1 | Class HGB 1 | Class HGB 2 | Class HGB 3 |
| Acc. to EP | Type 1 | Type 1 | Type 1 | Type 111 | Type 111 |
| Acc. to USP | Type 1 | Type 1 | Type 1 | Type 111 | Type 111 |
| Acid Resistance (DIN 12116) | Class S1 | Class S1 | Class S1 | Class S2 | Class S1 |
| Alkali Resistance (ISO 695) | Class A2 | Class A2 | Class A2 | Class A2 | Class A2 |
Temperature Resistance
3.3 Expansion borosilicate glass, has excellent thermal properties at both high and low temperatures. The maximum recommended working temperature for laboratory glassware 3.3 expansion borosilicate glass is 500°C (for short periods of time only). Special care should be taken at temperatures above 150°C to ensure both heating and cooling is achieved in a slow and uniform manner. 3.3 Expansion borosilicate glass also performs excellently at lower temperatures and can withstand conditions down to approximately -192°C making suitable for use with liquid nitrogen. In normal laboratory use, temperatures of -70°C are easily sustained for lengthy periods. Again special care should be taken to avoid sudden changes in temperature, and cooling should be achieved in a slow uniform manner.
Optical Data
Borosilicate glass is clear and colourless in appearance and thus transmits light through the visible range of the spectrum. This quality makes it ideal for work involving photochemical reactions, for example, chlorinations. The graph (below) shows the degree of transmission of light as a function of wavelength in the ultra-violet, visible and infra-red regions of the spectrum. For the majority of glassware detailed in our catalogue, the thickness of the glass is 2 – 5mm.
Amber Coated Glassware
Several DWK Life Sciences products, including media-lab bottles and volumetric flasks, are available in amber-coated glass. The glassware is coated on the exterior surface with a brown diffusion colour which results in a strong absorption in the short wavelength region up to 500nm. This feature is particularly useful when handling reagents that are light-sensitive.
Centrifuge Tubes
DWK Life Sciences can supply a number of branded centrifuge tubes. We advise the maximum Relative Centrifugal Force (RCF) they can be subjected to within the specific product information. Before centrifuging, it is important to calculate the actual RCF values that will be generated. This can quickly be determined by using the following nomogram. To calculate the RCF value at any point along the tube, measure the radius, in mm, from the centre of the centrifuge spindle to the particular point.
NB: The chosen point should be the base of the tube as this area will experience the maximum RCF.
Note the radius value from the right of the table and draw a line to the appropriate centrifuge speed value on the left hand column. The RCF value is the point where the line crosses the centre column.
The nomogram is based on the following equation:
RCF = (11.17x10-7) RN2
R = Rotational radius (in mm)
N = Rotational speed (in RPM)
The allocated RCF values are for tubes in good condition. Do not use centrifuge tubes which are scratched, abraded or chipped as the strength will be seriously impaired.