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Cooling baths are generally one of two types: (a) a cold fluid (particularly liquid nitrogen, water, or even air) — but most commonly the term refers to (b) a mixture of 3 components: (1) a cooling agent (such as dry ice or ice); (2) a liquid "carrier" (such as liquid water, ethylene glycol, acetone, etc.), which transfers heat between the ...
Because the liquid-to-gas expansion ratio of nitrogen is 1:694 at 20 °C (68 °F), a tremendous amount of force can be generated if liquid nitrogen is vaporized in an enclosed space. In an incident on January 12, 2006 at Texas A&M University , the pressure-relief devices of a tank of liquid nitrogen were malfunctioning and later sealed.
This Wikipedia page provides a comprehensive list of boiling and freezing points for various solvents.
Nitrogen, argon, helium and other inert gases are commonly used. To maximize this process called sparging, the solution is stirred vigorously and bubbled for a long time. Because helium is not very soluble in most liquids, it is particularly useful to reduce the risk of bubbles in high-performance liquid chromatography (HPLC) systems.
Two procedures for degassing are common. The first is known as freeze-pump-thaw — the solvent is frozen under liquid nitrogen, and a vacuum is applied. Thereafter, the stopcock is closed and the solvent is thawed in warm water, allowing trapped bubbles of gas to escape. [4] The second procedure is to simply subject the solvent to a vacuum.
During the final stage of freezing, an ice drop develops a pointy tip, which is not observed for most other liquids, and arises because water expands as it freezes. [8] Once the liquid is completely frozen, the sharp tip of the drop attracts water vapor in the air, much like a sharp metal lightning rod attracts electrical charges. [8] The water ...
Typically, a sample is plunged into liquid nitrogen or into liquid ethane or liquid propane in a container cooled by liquid nitrogen. The ultimate objective is to freeze the specimen so rapidly (at 10 4 to 10 6 K per second) that ice crystals are unable to form, or are prevented from growing big enough to cause damage to the specimen's ...
Snap-freeze is a term often used in scientific papers to describe a process by which a sample is very quickly lowered to temperatures below -70 °C. This is often accomplished by submerging a sample in liquid nitrogen .