What Is The Difference Between A Liquid Nitrogen Cylinder And A Dewar?

What is the difference between a liquid nitrogen cylinder and a dewar? This is a question that often comes up when discussing cryogenic storage of biological samples or other materials that require extremely low temperatures. While both a liquid nitrogen cylinder and a dewar are used for storing liquid nitrogen, there are distinct differences between the two.

**Construction

A liquid nitrogen cylinder is typically made of aluminum or steel and has a storage capacity of up to 50 liters. It is designed to hold liquid nitrogen under pressure and has a valve for dispensing the liquid. In contrast, a dewar is a double-walled container that is made of glass or metal and is used for the storage of liquid nitrogen. The inner wall is made of a material that can withstand extremely low temperatures and the space between the inner and outer wall is often evacuated to minimize heat transfer.

**Capacity

One of the key differences between a liquid nitrogen cylinder and a dewar is their storage capacity. While a liquid nitrogen cylinder can hold up to 50 liters of liquid nitrogen, a dewar can only hold a fraction of that amount. Dewars are typically used for smaller scale storage, with capacities ranging from 2 liters to 10 liters.

**Dispensing

Another difference between a liquid nitrogen cylinder and a dewar is the way in which the liquid is dispensed. A liquid nitrogen cylinder can dispense liquid either through a fixed pipe or a flexible hose, depending on the design of the cylinder. A dewar, on the other hand, is not designed to dispense liquid directly. Instead, the liquid is typically transferred from the dewar to a smaller container or cryovial for use.

**Cost

Cost is another factor to consider when choosing between a liquid nitrogen cylinder and a dewar. Liquid nitrogen cylinders are generally more expensive than dewars, due to their larger capacity and higher pressure rating. Dewars, on the other hand, are a more economical option for smaller scale storage.

**Portability

One advantage of a dewar over a liquid nitrogen cylinder is their portability. Dewars are often designed to be easily transportable, with features such as sturdy handles and wheels. This makes them ideal for use in the field or for transporting samples between different locations. Liquid nitrogen cylinders, on the other hand, are often bulky and difficult to transport.

**Safety

Safety is an important consideration when working with liquid nitrogen. Both liquid nitrogen cylinders and dewars can pose potential hazards, such as the risk of explosion or asphyxiation if handled improperly. However, liquid nitrogen cylinders are typically subject to stricter safety regulations due to their higher pressure rating and larger storage capacity.

**Applications

The choice between a liquid nitrogen cylinder and a dewar often depends on the specific application. Liquid nitrogen cylinders are often used for larger scale storage of biological samples or other materials, such as semen or embryos. Dewars, on the other hand, are typically used for smaller scale storage or for transporting samples between different locations.

**Conclusion

In summary, while both a liquid nitrogen cylinder and a dewar are used for storing liquid nitrogen, there are distinct differences between the two. Liquid nitrogen cylinders are typically made of aluminum or steel and have a larger storage capacity, while dewars are smaller and more portable. Liquid nitrogen cylinders are also subject to stricter safety regulations due to their higher pressure rating. The choice between a liquid nitrogen cylinder and a dewar often depends on the specific application and the scale of storage required.