pleochroism

Pleochroism occurs when a crystal absorbs light differently along different orientations within the crystal. Meaning, when looking down one axis of the crystal, light enters randomly polarized (there is no preference for the direction that the amplitudes of the waves are travelling). As the light passes through the crystal, only light which is in a particular orientation is absorbed, allowing other light to pass through. When this occurs for a particular band of visible light, you get crystals that are differently colored when viewed along different directions. This is all very confusing. The best explanation I could find on the web after a brief search is still a bit confusing, but much more elegantly worded with a touch of bad grammar. They're Spanish, so I will give them a free pass. I cut some tiny pieces of the crystal with a razor and tried to line them up so you can see the two different colors. These two crystal fragments (right) were cut from the same single crystal (largest crystal from the left picture). These are technically dichroic because they display only two colors, although pleochroism would only be used for crystals which displayed three different colors, but this is never called "trichroic" for some reason.

red or green?

The crystals diffract. It has been really difficult figuring out just what color these crystals are. The compound is paramagnetic, so the color is very deep. It looks like a reddish purple color when it is in solution, but the crystals came out almost with a green color when looked at the right way. I took them to the crystallographer who informed me that the crystals are dichroic, and this explains the confusion in the colors. For now, a crummy picture of the crystals and one of the diffraction slices... later, hopefully, pictures showing the dichroism and little more discussion on just what dichroism is and how it works. A resounding success by any measure. X-ray quality crystals were grown from a slowly cooled n-hexane solution.

Soxhlet success!

The extractor did wonderfully. The green substance from a couple posts ago was much less pure than I had hoped, consisting mostly of a blue substance (identity yet unknown, but not starting material.) There are three pretty distinct colors here, the yellow substance in the top sample tube is the desired product. The bottom tube is the mystery blue compound. I feel like I should spend a little time figuring out what this is so that I can avoid making it in the future. The middle tube is the original sample from the crude mix, composed of both compounds. I forget whether or not I had claimed the green compound in my color checklist, but if I did, it was unwarranted. Instead, I have made a yellow compound (which I can claim) and a blue compound (which I am not claiming yet as it is not properly identified.)