Glassware has become ubiquitous in laboratory experiments thanks to its many favourable qualities.
It is inert, transparent, is chemically and heat-resistant, and available in a wide variety of shapes and sizes. From round-bottom flasks and fractionating columns to condensers, bubblers and extractors, laboratory glassware serves many functions.
This is especially true when the pieces are connected together to form the assemblies associated with the classic techniques of organic chemistry. Distillation, extraction, filtration and reflux processes all require different complexities of laboratory glassware assemblies and while many of the scientists who helped develop these techniques had to resort to custom-made glassware, bungs and rubber tubing to connect items, the invention of interchangeable jointed glassware has meant many more – and safer – options are now available.
In this blog, we will look at the various types of jointed glassware available, where each type is most commonly used, and explore some basic techniques for its safe maintenance.
Types of Jointed Glassware
The use of jointed glassware helps to avoid spills and leaks of potentially harmful and often valuable substances during experiments.
However, while its benefits are clear it is important you select the right type of jointed glassware for the process you are carrying out.
There are a number of different types of joints, each with its own specific functionality.
These are the most common type of ground glass joint and feature a tapered cone and socket. Sockets of this kind often feature a rounded rim profile, which gives additional strength to the joint while also making them less prone to chipping than a square rim profile.
Spherical joints should be used for techniques where some flexibility in the angles of the glassware being joined together is required. They are commonly used to connect receiving flasks to rotary condensers, for example, whose weight can increase significantly as the flask fills. The spherical joint allows the flask to be connected to a sloping condenser at a vertical angle, thus reducing the strain placed on the joint.
Flange joints, or butt joints, are used to provide straight-line connections along with assemblies. This type of connection is commonly used for pipeline constructions and on large capacity flasks and reaction vessels. The ability to use wider flange joints provides easier access to the contents of flasks and tubes.
Screw Thread Joints
Screw thread joints provide a strong but easily adjustable connection. They are ideal where the length of an assembly might need to be varied, and a sliding joint can be employed to achieve this. Double-ended screw cap glassware is also commonly used, enabling lines to be adjusted from either side for even greater flexibility.
The Quickfit® Jointed Glassware Range
DWK Life Science’s Quickfit® portfolio is an example of a jointed laboratory glassware range, containing more than 1,000 products and a full range of the joint types listed above. Pioneered in 1934, Quickfit® interchangeable ground glass joints are suitable and safe to use in a wide range of lab applications, with a variety of acids, alkalis and solvents over a broad temperature range thanks to its PYREX® borosilicate glass composition.
The use of a unique two-stage joint grinding process to produce a super-fine joint surface finish means that a leak-proof, vacuum-tight and safe seal is created, preventing liquids and gases from leaking from joints in the glassware apparatus.
Safe Operation for Jointed Glassware
As with all laboratory glassware, there are some basic steps you need to follow to ensure the safe, sustainable use of jointed glassware:
- Wash new glassware before first use to avoid contamination from packaging fibres
- Examine glassware to ensure it is not scratched, chipped, cracked or etched as any defects will reduce the mechanical strength of the glassware and may cause it to break during use
- Whether transferring or using glassware, be careful not to scratch it, force it or handle it at the weakest points
When using interchangeable jointed glassware, there are other considerations for use:
- While silicone grease may be used to help seal a joint, Quickfit® joints are designed to be used without it to avoid contamination. A cleaner and non-contaminating alternative is the use of a PTFE Joint Sleeve that fits between the cone and socket joints
- Always check the maximum temperature guidelines for the equipment you are using. Although the maximum recommended temperature for Quickfit® glassware is 500 °C (for short periods only), the working temperature for other items – plastic connections, stoppers, tubing, etc, – could be much lower
- When using temperatures above 150 °C, heating and cooling should be carried out in a slow and uniform manner to avoid breakage by thermal shock
- If using a hotplate, ensure that the top plate is larger than the base of the vessel to be heated. And never put cold glassware onto a pre-heated hotplate
- When using a Bunsen burner, employ a soft flame and use wire gauze with a ceramic centre to diffuse the flame
- This will avoid ‘hot spots’ developing in the glass, which could cause it to break
- Do not apply high temperature or heat sources directly to any item of volumetric glassware as this will impair the volumetric accuracy
- PYREX® borosilicate glass is microwave safe, but you must also ensure the contents and any attachments are as well
- Always wear appropriate PPE when conducting any laboratory experiments and always use any available safety equipment – safety screens, safety cages, etc. Like all equipment within the laboratory environment, it is important to know how to use jointed glassware safely, securely and consistently in order to get the best out of the products you choose
The information in this article has been provided by DWK Ltd.
For further information on this range, please visit our selection of Quickfit® products.