Reef Chemistry Question of the Day #161 Using a Syringe

[Robink]

B

 

[joshkirkland83]

No, the process is totally independent of the tip size for any syringe.

Uh oh, so my parameters are waaaaay off. I understand how its 2.9. Well played sir, well played.

Syringe tips always have some air when you start. The amount of air depends on the tip size. But it has no impact on the volume of liquid drawn in or dispensed.

 

[Paul B]

If you push the plunger all the way in, all of the liquid will be dispensed. Probably on your foot if you are watching the plunger instead of where you want to dispense it.

 

[Habib(Salifert)]

I've estimated the drops from the Salifert tips to be appx. 0.02 mL, whereas the drops from my 50 mL Class A burette are more like 0.058 mL. When I'm going for the greatest resolution possible on a titration, I aim for the total amount of titrant to be at least 15 mL, and use the burette up until the last 0.5 mL or so, and then use a Salifert syringe with tip for the last portion of the titration because of the nice, small drop size!

It is typically 0.014 ml.

 

[JimWelsh]

It makes even smaller partial drops, too.

 

[alten78]

Looks like a lot of folks parameters are off! 2.9ml!

We should probably go over how to properly measure liquid in a container and which part of the meniscus to use, if it already wasn't a question

 

[JimWelsh]

There is no meniscus involved in this measurement.

 

[alten78]

My point was, if so many people are getting this wrong, they are probably getting how to measure when a meniscus is involved as well.

 

[ThePriceSeliger]

Gotta say, this is so fun to follow along.

Lot of people here took a number of science classes but apparently some did not quite take enough, lol. Just love the various rationales for the wrong answer, heck even the thinking for the right answer is absolutely humorous.

That syringe is remarkably accurate and assuming the tip was attached tightly and the plunger wasn't pulled back too quickly, the answer is 2.9

This. Thank you.

 

[Randy Holmes-Farley]

My point was, if so many people are getting this wrong, they are probably getting how to measure when a meniscus is involved as well.

Not exactly what you are asking for, but here's the previous question, which has a meniscus:

https://www.reef2reef.com/threads/r...loating-glass-hydrometer.226121/#post-2620144

 

[markalan]

B 2.9

 

[smh254]

If it's not 2.9 I've been doing it wrong for years

 

[DeniseAndy]

Very curious as to the answer. I know with test kits, they are set up to ignore the air and fill to the line (2.9). This is not the same thing as saying the amount of liquid is a specific answer (1.6).

In medical field, we would flip the syringe around and make sure no air is in the syringe. By doing this, the amount of liquid would be only 1.6ml. However, when it comes to our standard testing in reef keeping, they take that air into consideration when making the test kits because most people do not flip and get air out and saves a step.

I firmly believe that it is consistency and not a number you should be worried about. If you do the test ten times the same way, you should get the same answer. So, stick with your method. If you need to know exacts (something is really wrong) go for a triton test. If you are consistent, you can still tell whether you have had lower calc or lower mag or a swing in alk no matter what method you use.

 

[Randy Holmes-Farley]

I firmly believe that it is consistency and not a number you should be worried about. If you do the test ten times the same way, you should get the same answer. So, stick with your method. If you need to know exacts (something is really wrong) go for a triton test. If you are consistent, you can still tell whether you have had lower calc or lower mag or a swing in alk no matter what method you use.

Well, there's a huge difference between 1.6 and 2.9. That would be equivalent to 420 ppm calcium vs 760 ppm calcium, or 1280 ppm magneisum vs 2320 ppm. I would not want to stick with the wrong method.

 

[redfishbluefish]

..........In medical field, we would flip the syringe around and make sure no air is in the syringe......

The reason you flip this over in the medical field...to eliminate the air....is because you don't want to take the chance of injecting air into someone's arteries or veins. That just might be problematic!

 

[saltyphish]

You are still pulling in the same volume the syringe shows measured. Answer 2.9

 

[joshkirkland83]

Well, there's a huge difference between 1.6 and 2.9. That would be equivalent to 420 ppm calcium vs 760 ppm calcium, or 1280 ppm magneisum vs 2320 ppm. I would not want to stick with the wrong method.

Randy, can we get an answer before my coral dies?

 

[DeniseAndy]

I meant consistency as in your numbers. If you are getting a really wacked reading in the first place it seems obvious to check your method. However, if you get a within range answer and you continue to use that method each time, that is consitency. Then you can learn from differences what is going on. Also, if nothing is going right and nothing is thriving and such, you do need to check your numbers.

Yes, I am aware that air is bad in a syringe. However, the amount of liquid in the syringe is read differently when you remove the air. In this case it would be read on the black mark after the cone. 2.9 If we were to take that same syringe, turn upside down, knock out air bubbles, it would read 1.6 once air was removed. That is all I was trying to say.

 

[jason2459]

I find reading through this thread has given me a mix of interest, concern, and humor.

 

[reefaboo]

B. 2.9 ... answer please