What Are the Physics Behind Drawing Up Medication in a Syringe?

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Discussion Overview

The discussion explores the physics involved in the process of drawing medication into a syringe, including the roles of air and pressure dynamics during the procedure. It addresses both theoretical and practical aspects of the process.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant asks for clarification on the physics behind the entire process of using a syringe to draw up medication.
  • Another participant suggests that introducing air into the syringe helps to prevent a partial vacuum from forming in the vial, facilitating the withdrawal of the liquid medication.
  • A different participant argues that air is not pulled into the syringe but rather pushed in, emphasizing the pressure dynamics involved and the limitations of vacuum pressure.
  • One participant uses a metaphor to describe the challenge of managing air molecules during the process, likening it to herding cats.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics of air movement in the syringe, with some agreeing on the necessity of air to prevent vacuum formation while others contest the nature of how air enters the syringe.

Contextual Notes

The discussion does not resolve the specifics of air dynamics or the implications of pressure differentials in the syringe system, leaving some assumptions and definitions unaddressed.

tillitea
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Can someone discuss the physics behind pulling air into a syringe, inserting needle into med vial, expelling the air, and finally drawing up medication. This process makes it easier to draw up the liquid med as opposed to simply inserting needing and drawing up med. Thank you.
 
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It provides a volume of air to replace the volume of liquid being withdrawn from the med vial. Without this, the withdrawal of the medical would be producing a partial vacuum in the vial.
 
Air is never pulled into the syringe, only pushed in. Air goes from higher concentration to the void you are creating inside the syringe.

If you put a vacuum gage on the syringe,(no matter how long the syringe was), The pressure differential would never exceed 14.7psi.(Sea Level)
 
Last edited:
Yes, it is just a bit hard to corral those molecules and drag them in. You just have to let them follow at their own pace. Just like herding cats!
 

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