Red Sea Test Question

[USMC 4 LIFE]

When drawing regent from my Ca, Alk, Mag Test kits, there is always an air bubble between the regent and plunger in the syringe. So my question is what would this image be read as? 10 or 8?

 

[Havoks]

8. When you do the tritation just substract what is left from 8, or whatever you started with.

 

[USMC 4 LIFE]

So the air gap doesn’t compensate for the extra fluid on the tip of the syringe.

 

[K. Steven]

This looks like the syringe for drawing the water sample, not the reagents. The reagent syringe has 0.1 mL markings.

Make sure to push all the air out while submerged so you have no air in the syringe and pull the bottom of the plunger to the designated volumetric mark.

 

[USMC 4 LIFE]

That’s correct. I just used that syringe as an example.

 

[K. Steven]

If you're talking about the air space in the colored syringes, that's the air in the syringe tip. This is compensated for and the bottom of the plunger should be at the 1.0 mL mark before beginning the titrations.

 

[Larry L]

So the air gap doesn’t compensate for the extra fluid on the tip of the syringe.

Yes, that's exactly what is happening. When you start with the plunger at zero, there is some air in the tip. When you pull the plunger up from zero to 1.0, you are pulling in 1.0 ml of liquid, and the air that was in the tip ends up at the top. But you still have 1.0 ml of liquid in the syringe. So you should read that as 1.0, not 0.8.

 

[K. Steven]

Yes, you read the marking where the bottom of the plunger is. In this example, 0.65 mL of titrant was used.

 

[USMC 4 LIFE]

Thanks!

 

[kamike91]

You read from where the black plunger is, which is 10. The air is just what fills the tip when the plunger goes all the way down.

 

[Randy Holmes-Farley Verified Community Expert]

We discuss these issues in great detail here:

Reef Chemistry Question of the Day 161 Using a Syringe
https://www.reef2reef.com/threads/reef-chemistry-question-of-the-day-161-using-a-syringe.226267/

 

[USMC 4 LIFE]

We discuss these issues in great detail here:

Reef Chemistry Question of the Day 161 Using a Syringe
https://www.reef2reef.com/threads/reef-chemistry-question-of-the-day-161-using-a-syringe.226267/

Thank you all!

 

[sghera64]

When drawing regent from my Ca, Alk, Mag Test kits, there is always an air bubble between the regent and plunger in the syringe. So my question is what would this image be read as? 10 or 8?

10.

Not 8. Not 9.8

Like what has already been shared, the syringe measures displacement. So long as you sucked up (negative displacement) NO air, then you will displace 10mL if you return the plunger to zero.

Note read the scale where the ring of the plunger contacts the barrel wall do not try to read where that point in the center of the plunger is. As a check when fully depressed, look what part of the plunger is touching the 0 line on the barrel.