How many drops in a ml? Does size matter?!

[Tetsab]

Hello all, three weeks in but still just a beginner and far from an expert so thought I'd start my first-ever thread here in the 'innocents quarter'.

Having seen various quotes on various threads as to how many drops constitute a millilitre, 20, 30 etc I've got to ask what seems an obvious question now I've got myself all puzzled.

I have three different bottle sizes - 3.7ml testers from Johnson's Creek, really teeny weeny bottles. Really teeny weeny droppers as well. Do fit nicely in my old cigarette case, though.
A 15ml bottle from Smokester (e-cigs.co.uk) which has a larger and quite intricately-made dropper.
A 30ml bottle from Totally Wicked - even BIGGER but straightforwardly-made dropper.

Surely there will be different numbers of drops from each of these droppers to make a millilitre so it actually depends on what size bottle you've got? If I'm topping up a cartridge I can get about 10 drops from the JC dropper into it before it starts looking full again but only need two or three from the TW dropper.

I am interested because I know on the continent they dispense medicines in dropper bottles with instructions to use 'X' number of drops for a dose so had always assumed it was a standard measurement but now I'm not so sure!

I'm sure all the guys will tell us that size matters, but being a girl I've always thought that wasn't the only criterion...

 

[ZambucaLu]

Hi Tetsab. I had a similar question. People will say something like "just put 2 or 3 drops on the atomizer, but be careful not to flood it". Well, right now I am using a little plastic 10ml bottle where I had to snip off the top. The drop from that is a lot smaller than the 35ml bottle I have where the hole was already made. So I can't really tell how much I'm using yet.

Are most eyedropper holes a standard size and is that what people are talking about when they say "a drop"? It's not a big issue for me but it was something I thought about.

I can't recall how many drops they said were in a ml but I can guarantee that the little pinhead opening I have in my small bottle would not equal the drops they are talking about.

Lu

 

[BarryK]

It just occurred to me that if you see how many drops you can get into a teaspoon - that's gonna be within a knats **ck of 5 millilitres.

Better still, a plastic medicine spoon is spot on 5mil ..............

Barry

 

[usehername]

There are 180 drops in a 3.7 ml bottle of JC using the supplied dropper.
It takes 146 drops from the typical plastic squeeze bottle to fill the same 3.7 ml bottle.
Interestingly, using a JC dropper instead of the squeeze bottle it will take 190 drops to fill that 3.7 ml bottle. The contents of the squeeze bottle is typical Chinese fluid. somewhat thicker than the JC juice.

 

[usehername]

Sorry .. cant edit.. If you split the difference in viscosity to 185 drops in that sample bottle you get 50 drops per ml.

 

[ApOsTle51]

correct, all depends in the viscosity of the liquid becuase i'm sure gravity and surface tension limits are the same where ever you are in the world.

If you used the same liquid but a different dropper, drop size will remain exactly similar

 

[Tetsab]

Ye gods, Usehername - did you actually COUNT to find that out to such precision??? ...and I thought I could be a bit OCD at times!! If so, my gratitude for your dedication to finding out the truth.

ApO, I think I understand what you're saying about the viscosity making a difference, although it seems a big difference between the JC and the TW I have here at home. Does this indicate that TW is MUCH thicker? That would mean that number of drops per ml would vary according to the brand of liquid you're using, so this might account for the difference between the figures people are quoting. Imagine it gets even worse when you make up your own mixtures.

My reading of Usehername's figures was that three tests were carried out with the result that 3.7ml of JC was 180 drops, but the other two were BOTH with the Chinese liquid and gave different results, 146 drops with the squeeze bottle but 190 with the JC dropper.

I had kind of thought that maybe the size of the dropper's aperture might affect the size of drop? Because although surface tension might be the same (unless you're on top of a mountain, maybe?) there is less glass for the drop to 'hold on' to with a smaller opening so a spherical drop would form and fall that much sooner? My Physics & Chemistry 'O'-Level seems an awfully long time ago so I quite accept I'm probably talking c**p!

Ho hum, could waste centuries considering these matters of very small moment...

 

[usehername]

Correct Tetsab. The second and third measures were with the same chinese fluid. First out of the common plastic squeeze bottle and finally with the JC dropper.
Not sure why I do these things...

 

[Kate]

I found this

"According to Webster dictionary, "drop" indicates the smallest volume of a liquid that may be measured. The size of drop may vary with the viscosity of the liquid."

Drop (unit - Wikipedia, the free encyclopedia)

 

[Bertrand]

I would have thought density, surface tension and dropper diameters would be the deciding factors. My speculation is that at the point the downward force due to gravity (dependent on liquid density) overcomes the upward force due to the liquid's tendency to cohere (dependent on surface tension and dropper diameter) the drop would break off.

I don't see how viscosity would really come into play except in extreme cases like glass "droplets" (you'll be waiting a while for them to form...)

 

[Sexi]

Medically speaking 5 drops=1cc, (cc same as ML). 5ML=1teaspoon. Hope this helps answer your question some.
Hugs,
Teresa

 

[Tetsab]

Hi Theresa, thanks for joining in.

I thought I'd quote the whole Wikipedia article which Kate found as it is really interesting - looks like opinions as to what constitutes 'a drop' can vary a lot. Hope Wikipedia doesn't mind, it has been credited.

One bit that caught my eye and worries me a bit was the pharmacists deciding to 'go metric' and apparently rather arbitrarily deciding that 20drops=1ml. Even if their 'equipment' has been standardised (ie dropper size) the viscosity and density of the fluid itself can still cause variation in quantity. Let's hope not too many medications are compounded using the 'drop' as a quantity any more!

Overall think my personal conclusion has to be that a 'drop' may not be a really useful standard measurement in connection with e-liquird, and size DOES matter!

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From Wikipedia, the free encyclopedia

(Redirected from Drop (unit))
Jump to: navigation, search
For other uses, see Drop.
The drop is a unit of measure of volume, the amount dispensed as one drop from a dropper. It is often used in giving quantities of liquid drugs to patients, and occasionally in cooking.
The volume of a drop is not well-defined: it depends on the device and technique used to produce the drop and on the physical properties of the fluid.

There are several exact definitions of a "drop":

• the "metric" drop, 1/20 mL (50 μL).
• the medical drop, 1/12 mL (83⅓ μL).
• the Imperial drop, 1/36 of a fluidram (1/288 of an Imperial fluid ounce, or 1/1440 of a gill) (approximately 99 μL).
• an alternate, possibly apocryphal, definition of the drop is 1/1824 of a gill (approximately 78 μL).
• the U.S. drop, 1/60 of a teaspoon or 1/360 of a U.S. fluid ounce (approximately 82 μL).
• an alternate definition of the U.S. drop is 1/76 of a teaspoon or 1/456 US fl oz (approximately 65 μL).

According to Webster dictionary, "drop" indicates the smallest volume of a liquid that may be measured. The size of drop may vary with the viscosity of the liquid.
In the past, a drop was another name for a minim. This meaning was used in Pharmacy to describe a volume equal to one 60th of a fluid dram or one 480th of a fluid ounce. This is equal to about 61.6 μL (U.S.) or 59.2 μL (Britain). Pharmacists have since moved to metric measurements, with a drop being rounded to exactly 0.05 mL (that is, 20 drops per milliliter). In hospitals, intravenous tubing is used to deliver medication in drops of various sizes ranging from 10 drops/mL to 60 drops/mL. A drop is abbreviated gtt, with gtts used for the plural. These abbreviations come from gutta, the Latin for drop.[1]
A drop can also be used less formally as a unit of volume in recipes. According to some older kitchen references, 24 drops = ¼ teaspoon. Using U.S. definitions, this makes the drop equal to about 0.051 mL, making it quite comparable to the pharmacist's drop.[1]

[edit] References

1. ^ a b "Russ Rowlett". How Many? A Dictionary of Units of Measurement. University of North Carolina (2005-07-11). Retrieved on 2006-09-07.

Retrieved from "Drop (volume) - Wikipedia, the free encyclopedia"

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[ZambucaLu]

Good research Tetsab!

Lu

 

[Bertrand]

Didn't really believe that stuff about viscosity. Had a google, and found this. The chemical engineer agrees with my speculation:

Is a drop of water from a dropper equal in volume to a drop of mercury from the same dropper?

 

[Tetsab]

Great stuff, Bertrand.

As I'd sort of felt that viscosity and surface tension ought to be related to each other, the article has reminded me that other factors can also affect this, eg adding a detergent to water reducing the surface tension of water significantly. So in fact density is the more important factor, but size of dropper aperture is still involved.

I'm sure I've seen somewhere here that e-liquid's density is supposed to be fairly close to that of water, which weighs 1mg/ml and e-liquid being just slightly more.

As for this being 'good research' Lu, don't think I can really take the credit for doing much more than raising the question. It's really been the respondents, from Usehername and the precision drop-counting tests onwards, who've done the actual work of the research! And then been kind enough to bring it back to us here in this thread.

...ahh, I love the internet when it works like this, like it's SUPPOSED to do.
Without all the scammers, spammers, creeps and crooks who pollute it to the detriment of us all.
Up against the wall with the lot of 'em!

Love and peace to all forum members - please imagine a smilie blowing a kiss!

 

[Bertrand]

Great stuff, Bertrand.

As I'd sort of felt that viscosity and surface tension ought to be related to each other, the article has reminded me that other factors can also affect this, eg adding a detergent to water reducing the surface tension of water significantly. So in fact density is the more important factor, but size of dropper aperture is still involved.

I'm sure I've seen somewhere here that e-liquid's density is supposed to be fairly close to that of water, which weighs 1mg/ml and e-liquid being just slightly more.

Propylene glycol is very similar to water in density, but differs substantially in surface tension. In the chemist's response, he assumed the same dropper, so didn't comment on diameter. I would think you would get bigger drops with a bigger diameter, though, since you provide a larger surface for the particles to cohere together.

...ahh, I love the internet when it works like this, like it's SUPPOSED to do.
Without all the scammers, spammers, creeps and crooks who pollute it to the detriment of us all.

You'd have a hard time trying to tie in a product to this discussion.

"Our e-juice is proven to be 15% more dense and comes fully surface tensioned."

 

[Bertrand]

I would think you would get bigger drops with a bigger diameter, though, since you provide a larger surface for the particles to cohere together.

Had a bit more of a think. Actually, the effect of the diameter probably depends on the surface tension. In relative terms, while high surface tension liquid will cohere more strongly to itself, low surface tension will adhere more strongly to the dropper itself. (Examine the meniscus).

So while the diameter will definitely play a part, I'm actually not too clear on the relationship and unfortunately don't have a large enough collection of droppers with various inner diameters and lip thicknesses to test.

 

[usehername]

I have seen a few stating 15 to 20 drops of fluid = one ml. That is not accurate with efluid and supplied droppers. That is closer to the amount in one mini cartridge. I get 16 in a one piece 901 cart (litecig) and I get 25 in a two peice 901 cart (smokless shop) That is one half of a ml.

 

[NathanS]

i get about 90 drops per ml using my syring w/ needle. they are probably the smalest drops you can get

 

[EonBlue]

If you don't want to answer my many questions, just clue me in on your average drop/strength/type per day.

So would 48-58 drops of 11mg Johnson Creek (sample bottle) a day be right under or close to an 11mg dosage? Since 11mg per 1.2ml with JC? That's not over-doing it?

10 drops before 12:30 today didn't seem like enough. Usually I'm fine by 5:00 when I leave work without smoking at all in those 4 ½ hours but it ended with a bad headache. Maybe my own fault for messing around with the medium and high stock carts over the last few days.

I used to to smoke 8-12 American Spirit Lights (1.4mg), or 16-22 Marlboro Lights, or use a 21mg 24 hour patch.

I also have medium 555 Kick Juice. Anyone know what the mg per 1ml is in that?

Sorry for being paranoid. I just don't want to OD or have nicotine binding to my muscles...ha...because I think I'm immune to that vomit feeling that I used to get when going overboard as a kid. Seems like i've been using my whole life. I know 2ml is the standard but not of what type or anything.