Chemistry - Is there a simple field test for heavy water?
Solution 1:
There's a very simple test for $\ce{D_{2}O}$ that springs to mind - ice cubes made with heavy water sink in light water. I assume you're talking about differentiating a glass of essentially pure heavy water from, say, tap water, in which case this test should work rather well and requires equipment no more sophisticated than a freezer, ice cube tray and some glasses.
Solution 2:
Mass. Heavy water is noticeably heavier then light water. Simply weigh an equal amount of each water and see which weights more.
Light water weights 1 g/mL (0.99700 g/mL at 25 °C)
Heavy water weights 1.107 g/mL at 25 °C
So if you have 100 mL you will see an 11 g difference, assuming pure samples.
(The Science and Technology museum in Ottawa actually has samples you can lift to feel this).
Solution 3:
If you don't have access to a freezer, you could allow sun light to pass through your glass vessels and then through a prism. The heavy water will absorb less orange red light and the difference might be observable.
One of these might help (not complicated).
P.S. I did not want to post this as an answer because I'm not sure if it's realistic but I can not see were to add a comment.
Solution 4:
(Completely untested since, sadly, I have no access to heavy water.) Slowly pour the contents of one glass into the other. The index of refraction of heavy water is 1.328, that of light water is 1.333. Not much, but maybe just enough to see the inhomogeneities. If the decanted glass's contents sink, it had the heavy water. Otherwise, light water.
But if you have even a cheap kitchen scale, that would probably be the better test, since the densities differ by about 10%, as opposed to the index of refraction, which differs by far less.
Or, just add a drop of food colouring to one of the glasses. Or a drop of milk. Just to help out with the contrast.
Do the test with just a small sample from each glass if you want to avoid contaminating the expensive heavy water.
Solution 5:
Old question, but in the interim Cody's lab has released this video (among others) on tasting heavy water. His conclusion was that $\ce{^2H_2}\ce{^{16}O}$ tasted sweeter than $\ce{^1H_2}\ce{^{16}O}$ but $\ce{^1H_2}\ce{^{18}O}$ didn't. He wasn't able to tell the difference after eating. Of course, chemists absolutely freak out at the suggestion that one attempt to identify chemicals by tasting them, normally an extremely dangerous practice.