[mana]

hi all
as you know Milikan experiment showed the charge and mass of electron, it is interesting to me why he used oil instead of other liquids such as water or ... in his experiment? does oil have any special character for this measurement?
thanks for your help

[Borek]

In practical terms: it doesn't dry out easily.

[AdiDex]

From my point of view there may be 2 reasons for doing so -:

1.Since we can't make 100% vaccuum , H₂O vapours are lighter than air , whereas oil is much heavier .
2. Ripping of electron from water (ionization of water) is much difficult (since very less electron density) or we can say positive charge on oxygen containing molecule is unstable . Where as in Oils are heavy hydrocarbons (there are lots of electrons around them) , Charge density will be low and Carbocations are stable than that of Oxygen .

If any error then please correct me .

[Borek]

2. Ripping of electron from water (ionization of water) is much difficult (since very less electron density) or we can say positive charge on oxygen containing molecule is unstable . Where as in Oils are heavy hydrocarbons (there are lots of electrons around them) , Charge density will be low and Carbocations are stable than that of Oxygen .

Some droplets had positive and some negative charge, so it is not a matter of ionization ease. Charge on the droplets is just a stray electron or two, not combined with any particular molecules. Sure, on microscopic level some molecules can be much more ready to accept it or give it away, but it doesn't matter here.

[AdiDex]

I've interrelated these lines from Mass spectrometry by electron impact.

"In electron impact (EI) mass spectrometry the molecule is bombarded with highly energetic
electrons that knock a weakly bound electron out of the molecule. If you think this is strange,
think of throwing bricks at a brick wall: the bricks can’t stick to the wall but can knock loose
bricks off the top of the wall. Losing a single electron leaves behind an unpaired electron and
a positive charge. The electron that is lost will be one of relatively high energy (the bricks come
from the top of the wall), and typically one not involved in bonding, for example an electron
from a lone pair."

I can be wrong if this won't happen in the case of ionization. Because those loose electron can't be just vanished after being ionized , they should go to other molecules .

[magicalatom]

Off the top of my head I can say:

1. Oil is non-polar
2. It is more viscous than water, hence like someone else pointed out less drying issues
3. Oil is also slippery
4. Oil even has flammable properties vs water

Just think of all the properties even the boiling points/melting points of the specific oil because not oils are the same depending on their hydrocarbon chain lengths.

Hope I helped some.  Goodluck.

hi all
as you know Milikan experiment showed the charge and mass of electron, it is interesting to me why he used oil instead of other liquids such as water or ... in his experiment? does oil have any special character for this measurement?
thanks for your help