http://imgur.com/a/NHEjG
It has a like a red rubber top. I couldn't unscrew the cap, so I guess the only way in is through he red part.
I can't risk wasting any. The bottle is so small so even a little waste is no good.
If you are looking at precision then the only way is to dilute it into a solvent, divide the solvent and extract it back. Or use specialist services and/or equipment.
If not, here are a few layman ideas...note the word layman:
If you want to avoid wastage then there is no way you would be able to drill a smooth tiny hole into elastic rubber. You should be able to cut off and remove the aluminium cap surround with a knife or such (cut it on a side and then pry it off). Be careful not to cut yourself though. Then the rubber bit should be like a cork on a wine bottle which you could remove by sliding a thin screwdriver on the side and pulling it off. Be careful not to shake out all the stuff on the floor though.
A grain of common table salt (not kosher) is typically about 0.3mg-0.5mg or ~400mcg. So you could extract a grain of salt on a tin foil and use it for comparison using a magnifying glass and your careful eye or some geometry (i.e. if you want one fifth by volume/weight the diameter has to be about 1.7 times smaller, etc).
All in all, not an easy task working with such lab precision quantities.
- - - Updated - - -
Just had another idea. You are looking at 1/1000 right.
So you could take the whole thing out carefully on a tinfoil. Divide by half, divide by half again then again then again and keep doing it 10 times in total. That will do it much more accurately than the previous idea I suggested of using the grain of salt. Use a couple of sharp blades to work with it on the foil
Keep windows closed, do not sweat and do not turn on the fan. If you have cold and are sneezing/coughing then wait to get well first LOL
Good Luck!
