Since when are mL's a unit of weight?
 

I ran by a CVS today to pick up some shaving gel, as the stuff I had at home was too large to pass the Kip's Zip muster.

I noticed one brand--Gilette, I believe--that came in a fairly small can. It was labeled "NET WEIGHT: 100mL / 3.4 oz."

I almost laughed out loud in the store. First, this is the WORST example I've ever seen of confusing weight and volumetric measurements; usually, the confusion is on the oz / fl oz end of things, not the mL end! Second, it's uber-convenient, it would seem, that the "weights" match the current TSA guidelines.

I also noticed that my normal travel shave gel, in the exact same size can I already have but which says "Net weight: 5.6 oz" or something like that (which is why I left it at home!) now says, "Net weight: 3.4 oz"

Seems like people are manufacturers are doing all they can to capitalize on Kip's Folly.

All the answers are here: http://imdb.com/title/tt0387808/

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Duh. 1 mL of H2 has the same mass as 1 mL of iron filings.

That would be volume, duh.

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;)

"Go away! I'm batin'"

Mass of 1 ml of H2 depends on the pressure. Volume of a gas, such as H2 is not a meaningful quantity unless pressure and temperature are also given.

You only need to know density. Pressure and temperature have influence over density, but the measurement needed is density.

which weighs more... a ton of feathrs or a ton of bowling balls ;) ask your favorite TSA agent that...

Correct, but do you know densities of agses at various pressures and temperatures?:D

I'm surprised in all this discussion nobody thought about using grams as a unit of weight, thusly -- milligrams or mg.

Sanosuke!

OP has a good point. For water at atmospheric pressure 1 mL = 1 gram, but mL is never a measurement of weight.

Strictly speaking, neither are Kg, g or mg.

Although technically, grams are a unit of mass. Newtons are the unit of force. ^

The imperial units of mass are either the slug or lbm (pounds mass).

Presumably, that's so even the most stupid liquid barker can tell. Like the guy at JFK who told people to throw away their liquids because they weren't labelled, so he "couldn't see what they weigh."

No, I'm not making this up.