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Volumetric Glassware
Laboratory glassware can be manufactured from Borosilicate and Soda-lime glass. Soda lime glass  is generally used for Class B products or where long term exposure to chemicals is unlikely. Class A Borosilicate volumetric glassware has superior thermal and chemical resistance and is better suited to glassware for storage of solutions, e.g. flasks. The use of  Class A borosilicate glass for volumetric glassware means accuracy is retained over a longer working lifetime than their soda-lime equivalents. With everyday use, volumetric glassware requires recalibration. Soda-lime glass items will generally necessitate twice as many recalibrations as items constructed from borosilicate glass. ASTM 542 and ISO 4787 international standards for calibration of laboratory volumetric glassware recommend that volumetric flasks are recalibrated at the following intervals (or sooner if chemical corrosion is observed): Borosilicate – 10 years; Soda-lime – 5 years. Inscriptions Volumetric glassware is manufactured and calibrated in accordance with international ISO requirements. All of our volumetric glassware is marked with a set of inscriptions in accordance with any specific standard associated with it.Tolerance Class A – Highest level of accuracy Class B – General purpose work calibrated to a lower level of accuracy
Graduation  marks on volumetric glass is graduated in ml (millilitres) in accordance with the ISO standard IN Calibrated to contain EX Calibrated to deliver Blowout Indicates that the last drop should be blown out Temp °C All  volumetric glassware is calibrated at 20°C Certification All Class A Works Certified glassware bears a serial number for identification and traceability.Glass Technical Information Â
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Laboratory Glassware[/caption]
Certification
Many volumetric products are available with certification. Certificates confirm that the product has been tested for compliance to the appropriate standard.
Works Certified Products
Class A Works Certified volumetric flasks, pipettes, cylinders and burettes are inscribed with an individual serial number and are supplied with an individual calibration certificate. Each certificate includes details of the actual volume, uncertainty estimation for the calibration and the required tolerance for compliance. Graduated pipettes, Measuring cylinders and burettes are calibrated at five separate points on the scale which is detailed on the certificate.
Batch certificatesÂ
Class A volumetric flasks should have batch certificates. The batch certificate contains detailed information pertaining to the specific production batch including average volume and standard deviation for the batch.
Re-calibration
Normally, volumetric glassware only needs re-calibrating after extensive or demanding usage, which may have affected the original accuracy.
Re-calibration is usually not necessary if:
The glassware is new but been in storage for some time. Age does not affect accuracy.
The glassware is only subjected to moderate temperatures such as cleaning in a washing machine or sterilising in an autoclave at 121°C.
The glassware has been used for less than 5 years with no repeated use of corrosive chemicals or strong acids/ alkalis.
However, recalibration should definitely be considered under the following circumstances:
The glassware is made from soda-lime glass and has been in use for 5 years.
The glassware is made from borosilicate and has been in use for 10 years.
The glassware has been subjected to temperatures in excess 150°C.
The glassware is frequently used with strong acids or bases.
There are any signs of chemical corrosion e.g. frosting of internal glass surfaces.
