Is there nitrogen or liquid nitrogen in the nitrogen cylinder?

Nitrogen cylinders come in both liquid and gaseous forms; the cylinder you are referring to is the one that holds gaseous nitrogen. The liquid is usually stored in Dewar-type containers.

The nitrogen cylinders in our lab are all filled with liquid nitrogen; I’ve even poured it out before. The mist in the air looks magnificent:P

150MPa？ ? ? ? ? What kind of bottle can withstand that high pressure? :funk: I. Specifications for 40L nitrogen cylinders: Hydrostatic test pressure of 22.5 MPa ； Working pressure: 15 MPa ； *The normal filling pressure is 12.5 MPa. Therefore, the typical internal pressure rating for a 40-liter nitrogen cylinder is 12.5 MPa. When in use, a \"reductor\" must be employed to adjust the pressure to the desired level for gas output. For the use of nitrogen, an \"oxygen regulator\" is generally used in place of a \"nitrogen regulator\". The pressure to be used should meet the requirements specified for the operating pressure in the \"operating instructions\" of the chromatograph (or other gas-using equipment, devices, or instruments). II. Is it in a gaseous or liquid state inside the bottle? For the same substance, once the temperature exceeds the \"critical temperature,\" no amount of increased pressure can cause it to liquefy anymore. The critical temperature is the highest temperature at which a substance can be liquefied. Regarding the original poster’s question, I would like to first understand the basic properties of nitrogen: critical temperature: -146.9 degrees Celsius; critical pressure: 3.394 MPa. At the critical temperature and critical pressure, there is no significant difference between the gaseous and liquid states ； Above the critical pressure, when the temperature drops below the critical temperature, everything turns into a liquid; there is no phase transition stage nor phase transition latent heat. The vaporization process in the reverse direction is the same. Therefore, under the conditions given by the poster, the bottle should contain gaseous nitrogen.

The 150MPA mentioned by LZ really scared me.

It’s liquid nitrogen, but the 150MPA value mentioned by the original poster is indeed impressive! With such great pressure, what kind of container is needed? :funk: It should be 15MPA, right?

Nitrogen cylinders (steel tanks) contain compressed nitrogen at normal temperature and high pressure; Dewar flasks provide good insulation and hold liquid nitrogen at normal pressure and low temperature (77 K, -196°C)

Properties of nitrogen: Critical temperature: -146.9 degrees Celsius; Critical pressure: 3.394 MPa. Based on the critical state, since the temperature is quite far from the critical temperature and the pressure ranges from 12 to 15 MPa, it is appropriate to classify it as a high-pressure gas. (Revising previous view) When temperature and pressure are close to the critical state, it may be a supercritical state. The supercritical state is not a normal state. Since the critical temperature of CO2 is relatively high, a supercritical state may exist at ambient temperatures. Last edited by Albertlu on 2009-2-22 15:46.]

Support for Floor 5! I work in this industry, and if the pressure in question is 15.0 MPa and the container is 40 liters in size, the gas must be in gaseous form inside the container. However, it cannot be denied that after multiple fillings of the bottle, some water will remain inside, but it is by no means liquid nitrogen.

Support for Floor 5! If the pressure is 15.0 MPa and it is a 40L steel cylinder, the gas must be in gaseous form inside the cylinder

I thought it was liquid? Through the discussions with these friends, I learned about it.

I thought it was liquid nitrogen; I was wrong!

When the conditions of critical temperature and critical pressure are exceeded, it becomes a supercritical fluid, a state in which gas and liquid are not distinct from each other. :) This post was last edited by zj333333 on 2009-2-22 18:59 ]

Thank you for the explanation on the 5th floor; I’ve learned something

Yes, according to everyone’s analysis, the result is already quite clear, as there are scientific figures to support it; it’s really enlightening.

Amazing! The analysis was really thorough. I also thought it was liquid nitrogen, but it’s not. I still think it’s liquid nitrogen :loveliness:

It should be in a gaseous state; liquid nitrogen has a very low temperature, and frost forms on the outside of the cylinder.

Additional note: So, is it possible to have liquid nitrogen filled in real life? Maybe. But that is mostly at normal pressure. For example, the liquid nitrogen tanks used for frozen semen at livestock stations. This tank is a atmospheric storage tank, and it should be insulated with a vacuum jacket inside. Some also have insulation on the outside. There are slight gaps around the seal at the top; the sperm are placed in a thin tube, which is then hung and inserted into the storage tank, where they are frozen using liquid nitrogen. The end of the rope passes through the gaps around the seal and leads outside, making it easy to retrieve the sperm. Additionally, the facilities where I study are limited; there are no liquid nitrogen tanks, so I will not provide any further details regarding that aspect. Those who wish to know it too, please help answer it as well. Looking forward to it.