Questioning the science of the volume of a liquid drop

[DeptOfMeteors]

I'm wondering if not all drops of the same substance are created equal. I'm finding that my FC is way above what I expect, and I think that part of the reason is that the drops are not all the same size. And I think that some might be too small because they are coming out too fast.
When I first invert my R-0871 bottle, several drops come out before I'm ready. I probably accurately count them withing 1 drop, but if they are too small, the sample will seem like it has more chlorine than it does.

 

[YippeeSkippy]

Don't squeeze the bottle. Let the drops drop naturally. See if that works better for you?

Maddie

 

[Jimrahbe]

D,

Let's see if Matt can fill us in on the science of using drops as a unit of measure. Calling @JoyfulNoise

Thanks,

Jim R.

 

[JoyfulNoise]

The fitment tips on the bottles should generate about 40uL per drop if gently squeezed and the drops are allowed to fall naturally.

Question - what size reagent bottles are you using, 0.75 oz or 2 oz ?

 

[ajw22]

The tip of the bottle is formed so a drop falls off of it at a certain size.

As was said let the drops fall from the tip naturally. Don’t squeeze the bottle to squirt any fluid.

 

[DeptOfMeteors]

For the 871, it's the bigger kind, so I'm guessing 2floz.

 

[Jimrahbe]

D,

I assume you are holding the bottle vertically, not sideways..

Jim R.

 

[DeptOfMeteors]

I definitely don't squirt--if I made a stream, there wouldn't be a question that the test was bad. But if I don't squeeze the bottle, it's going to fall out of my hand. It's going to take me some time to get the hang of this, but in the meantime, I'd like to know if the results I've had so far can be interpreted as overrated FC. Or have these bottles just not been benchmarked for this situation?

 

[DeptOfMeteors]

I assume you are holding the bottle vertically, not sideways..

Let's say more vertically than horizontally.

 

[JoyfulNoise]

I prefer the 0.75fl oz bottles honestly, they are easier to dispense droplets from. There is an unfortunate effect with the 2.0 oz bottles whereby the weight of the fluid is enough to push out a few droplets until the back pressure builds up to stop the droplets from coming out. It’s usually only a problem on new bottles when they are full and goes away with time. Then the bottles will only dispense when gently squeezed and you get good droplet uniformity. This happens with the larger bottles of R-0009 as well.

I’m not stingy with my reagents but then again I live where it’s easy to get Taylor products. Unfortunately Canada makes it more difficult kit.

Try your best. The dispense rate should be about 1 droplet per second. Any faster and you’re probably making drops that are too small.

 

[JamesW]

There is an unfortunate effect with the 2.0 oz bottles whereby the weight of the fluid is enough to push out a few droplets until the back pressure builds up to stop the droplets from coming out.

Before inverting the bottle, squeeze the bottle a little bit and then invert and you won't have that problem.

 

[Sunnydaze]

Before inverting the bottle, squeeze the bottle a little bit and then invert and you won't have that problem.

That's genius. I have the issue with my 2oz 0871 bottles. I'll be sure to remember that.

 

[SoDel]

Also, do not shake the bottle.