When I take a liquid into the syringe there is a bubble of air form the stem of the syringe. I presume that this bubble should be removed before the volume is read on the graduation, is this correct or does the volume measurement begin above the stem? I know you see doctors invert the syringe and give a little squeeze but I didn't know if this was just because of negative effects of air in the bloodstream. Thanks all you science geeks!
volume of syringe question
- Thread starter frantz
- Start date
if you measure the liquid, not the plunger stem the volume is dictated by the liquid, not the air space between liquid and plunger.
If you are referring the stem as the needle part, that volume is negligible as it's a real small hole in a tube. Still measure the liquid line in the barrel. 1/100 of a ml (in needle) should not have any effect either way.
If you are referring the stem as the needle part, that volume is negligible as it's a real small hole in a tube. Still measure the liquid line in the barrel. 1/100 of a ml (in needle) should not have any effect either way.
Stem volume is accounted for. The reason you see people "squirt" liquid into the air can be to release the air in the syringe, but, it is more likely to release the pressure in a prefilled syringe. I you don't release the pressure it can be harmful to the integrity of the vein. Oh, and...I play with syringes for a living...
When you draw up water in a syringe, and turn the syringe so that the tip is down, there is usually and "air slug" sitting on top of the water up to the rubber plunger tip. The way to measure the amount dispensed is to use the plunger tip as the point to read the starting and ending point on the syringe scale. If the plunger tip moves 0.2 on the scale, you have dispensed 0.2 of what is in the syringe. This will work as long as the air slug does not reach the tip, so that air is dispensed. So if you want to dispense 1.0 ml, use a 2 ml syringe. If all you have is a 1 ml syringe, dispense 0.5 twice using the above method.
Thanks for all the replies. It was a theory question more than application as the difference of a few drops of dosing don't make a huge difference in a 180g system. I wanted a better understanding of the tools I was using and ya'll provided it =-D
The reason air is dispensed out a syringe used on patients is to prevent the introduction of air. Syringes are not presurized. And remember, syringes used for medical purposes are only used once.
