To the main question: As others have said, how many ml in a dropper full depends hugely on the dropper! Better to get one from a child's vitamin bottle or something that has an actual volume mark on it. Or, ask the drugstore for a small syringe such as diabetics buy. 'Course, you might get a raised eyebrow walking into a strange drugstore to buy one syringe.
I was caught by CycloWizard's post (quote):
If you're an average person, you can stop reading. However, if you're an HT regular, the size of a 'drop' will depend on the substance you're dropping and the material that the dropper is made from. A drop is formed when surface tension forces between the fluid and the dropper exceed the shear forces of the fluid flowing down the dropper. Because the size of a drop is not constant, it's not necessarily correct to say that 20 drops is 1 mL. This correlation has been developed for water in most glass or plastic containers though and does stand up to muster as long as your materials are not too strange.
Reminds me of an experiment a buddy and I created during a summer job. We drew out a glass tube into a thin dropper tip, measured its internal diameter as best we could. Then we rigged it from a burette so a slow flow - drop by drop - of water came out. We collected the water drops and counted them for a while, then weighed the collection to get an average mass per drop. Dividing that by the cross-sectional area of the dropper hole (that is, the area of the column of water just as the drop broke free) with a conversion factor for mass gave us a measurement of the surface tension of the water. The answer was pretty damn close to reference values!
I was caught by CycloWizard's post (quote):
If you're an average person, you can stop reading. However, if you're an HT regular, the size of a 'drop' will depend on the substance you're dropping and the material that the dropper is made from. A drop is formed when surface tension forces between the fluid and the dropper exceed the shear forces of the fluid flowing down the dropper. Because the size of a drop is not constant, it's not necessarily correct to say that 20 drops is 1 mL. This correlation has been developed for water in most glass or plastic containers though and does stand up to muster as long as your materials are not too strange.
Reminds me of an experiment a buddy and I created during a summer job. We drew out a glass tube into a thin dropper tip, measured its internal diameter as best we could. Then we rigged it from a burette so a slow flow - drop by drop - of water came out. We collected the water drops and counted them for a while, then weighed the collection to get an average mass per drop. Dividing that by the cross-sectional area of the dropper hole (that is, the area of the column of water just as the drop broke free) with a conversion factor for mass gave us a measurement of the surface tension of the water. The answer was pretty damn close to reference values!
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