What are ground glass joints and their different sizes?

WHAT ARE JOINTS AND THEIR TYPES

 Due to the numerous advantages, glassware has become omnipresent in laboratory experiments.

It is chemically inactive, transparent in nature, is proven heat resistant and comes in a variety of shapes and sizes. Laboratory glassware is used for a variety of purposes, ranging from round-bottom flasks and fractionating columns to condensers, bubblers, and extractors. This is specifically true when the parts are linked together to prepare the assemblies connecting with classic organic chemistry techniques. While many of the scientists who contributed to the development of these techniques had to rely on custom-made glassware, bungs, and rubber tubing to connect items, the invention of interchangeable jointed glassware has resulted in many more - and safer - options.

In laboratories, ground glass joints are used to quickly and easily fit leak-tight apparatus together from interchangeable readily available parts. Using jointed laboratory glassware during experiments helps to avoid spills and leaks of potentially harmful and often valuable substances.

WHAT ARE THE DIFFERENT SIZES

Ground glassware joints can be ground to a repeatable taper or shape. They are designed to connect two pieces of glassware. An inner (or male) joint with the ground glass surface facing outward would be used on one of the glassware pieces to be linked, while an outer (or female) joint with the ground glass surface facing inward would be used on the other.

Inorganic chemists place a high value on keeping air and water out of reactions. As a result, many different types of glassware joints have been invented. There are numerous types of joints, each with its own unique set of capabilities. While the benefits are obvious, it is critical that you choose the correct type of jointed glassware for the process you are performing. The two most prevalent forms of ground glass joints are slightly conically tapered joints and ball and socket joints (at times known as spherical joints).

1. Conically Tapered Joints or NS Joint

This is the most common type of ground glass joint (these can also be carved out of quartz, steel etc.). When properly lubricated, the frosted, precision-ground glass surfaces produce a good compact seal and are exceedingly adaptable. A "male" (or "inner") joint is on the left, and a "female" (or "outer") joint is on the right. When the joint is connected, the inner one fits perfectly into the outer one, as shown below.

This type of socket frequently has a rounded rim profile, which adds strength to the joint while also making it less susceptible to chipping than a square rim profile.

2.    Ball and Socket Joints

 When the parts being linked require some flexibility, ball and socket joints are typically utilised. Due to the difficulties of aligning the two components, these are fairly prevalent on vacuum to mainly hold the traps. On the left, the socket is at the top, and the ball is at the bottom. A pinch clamp (for Safety purpose) is used to hold both the components together on the right if needed.

For approaches that demand some flexibility in the angles of the glasses being put together, spherical joints should be employed. They're typically used to link receiving flasks to rotary condensers, which can have a large weight increase as the flask fills. The spherical junction allows the flask to be connected at a vertical angle to a sloping condenser, decreasing strain on the connection.

WHAT ARE THE SIZE DIFFERENCE FOR US & UK

The size of a joint is defined by two numbers xx/yy, such as 24/29.

Ground Glass joint fittings:

24 – Diameter of the wide end of the ground joint (in millimetres)

29 – Length of the ground joint (in millimetres).

If you require the glasses to fit into existing glassware, make sure to check the joint sizes before you buy it. The majority of conical ground glass joints are made to meet ISO 383, European 'B' length joint size criteria. Jointed glassware is made to the American ASTM E-676 taper ground joint size specification.

EUROPEAN ‘B’ JOINT SIZES:

AMERICAN STANDARD TAPER JOINT SIZES:

 Also read: What are the uses of Condensers in the Laboratory?