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keaphon

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专业: 催化化学

[交流] [请教]用液氮和丙酮配混合溶液用来至冷的比例！

准备做化学吸附，需要－85摄氏度。文献上用液氮和丙酮配混合溶液来达到该要求，请问大牛：什么样的比例能达到零下85度啊！谢谢。

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五年后重新回归可研，自勉！

1楼 2008-10-23 20:50:45

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suhailan

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IPA/LN2

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An isopropyl alcohol (IPA)/liquid nitrogen (LN2) slurry is used to maintain cold trap temperatures of approximately -80 °C. Use the following instructions to mix such a slurry if this is the temperature you wish to maintain.
1.Chill a 600-mL dewar by rinsing it with LN2. Allow a small amount of LN2 to remain in the bottom of the dewar (approximately 1 cm deep).
2.Stirring constantly, slowly add approximately 500 mL of IPA. For greatest safety, use a laboratory squirt bottle. Squirt the stream of IPA along the inside edge of the dewar, very near the top, allowing the IPA to flow down the dewar’s inside wall. Do not stop stirring the mixture in the bottom of the dewar, even if stirring becomes difficult. As you continue stirring and adding IPA, the mixture will loosen and become easier to stir.
3.When all the IPA has been placed in the dewar, slowly begin pouring LN2 into the dewar. Approximately 1 liter is needed. You must continuously stir the mixture as you add the LN2. As ice chunks form, break them up and stir them down into the mixture. Avoid splashing. Gently knock ice chunks away from the sides of the dewar and continue stirring. Add liquid nitrogen until the slurry is within 25 mm (1 in.) of the top of the dewar.
4.Lift the stirrer out of the slurry and observe as the slurry drips into the dewar; the stirrer should be thickly coated with slurry.
Your goal is to achieve a slurry that has a thick, syrupy consistency without large chunks. When the slurry is cold enough, small pieces of ice may be present (10 - 20% of the mixture). A little ice accumulation along the sides of the dewar is acceptable.