If you are correct you have done me a favor. I thought that viscosity was determined, in part, by flow. Maybe I err, but I thought that if surface tension was reduced, the viscosity would also be reduced. Apparently, I stand corrected. - David LygaIn the case of aqueous solutions, droplet size is determined by the surface tension, not the viscosity. Wetting agents (surfactants) reduce the surface tension of water. The viscosity is unchanged.
If you read the link in post 19, you will find that the word viscosity does not appear anywhere in the description of how droplets form.
If you are correct you have done me a favor. I thought that viscosity was determined, in part, by flow. Maybe I err, but I thought that if surface tension was reduced, the viscosity would also be reduced. Apparently, I stand corrected. - David Lyga
it depends of course on the viscosity of the liquid but, for watery liquids, 12-16 drops equal roughly 1ml.Metric drops or Imperial drops?
Seriously, though, I've found droppers to be too inconsistent to be an accurate way of measuring anything, personally. Small syringes are my tiny measurement devices of choice.
right onThe physics is a bit complicated. How many angels can stand on the head of a pin? How many mice fill a bushel? Big mice, small mice, dried mice? Small volumes can be measured with a pipette or special automated dispensers sold by lab suppliers.
it depends of course on the viscosity of the liquid but, for watery liquids, 12-16 drops equal roughly 1ml.
If you read the link in post 19, you will find that the word viscosity does not appear anywhere in the description of how droplets form.
Thanks Ratty. I was under the impression that surface tension and viscosity had a relationship; evidently they never got together.
ising a lab micropipette could be a solution too.Thanks Ratty. I was under the impression that surface tension and viscosity had a relationship; evidently they never got together.
I found it interesting that the size of a drop from a given diameter tube remains (fairly) constant. That would validate my practice of using only one type of eyedropper for measuring liquid amounts in drops, after having calibrated it, of course. Changing to a different-size dropper would change the number of drops/ml. I intuitively assumed this, but never really researched it.
Really, if measuring drops from a calibrated tube-size is good enough for IV infusions, then it really should also be accurate enough for measuring the less-critical components of many photographic solutions, e.g., wetting-agent baths, small amounts of ferricyanide bleach from stock solutions, etc. We just have to calibrate our eyedroppers first to find how many drops/ml they deliver and make sure to hold them exactly vertically when dispensing our drops.
Best,
Doremus
I'd go with that.Don that's exactly what I found to be the answer, given the variables.
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