About this Author
DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: Twitter: Dereklowe

Chemistry and Drug Data: Drugbank
Chempedia Lab
Synthetic Pages
Organic Chemistry Portal
Not Voodoo

Chemistry and Pharma Blogs:
Org Prep Daily
The Haystack
A New Merck, Reviewed
Liberal Arts Chemistry
Electron Pusher
All Things Metathesis
C&E News Blogs
Chemiotics II
Chemical Space
Noel O'Blog
In Vivo Blog
Terra Sigilatta
BBSRC/Douglas Kell
Realizations in Biostatistics
ChemSpider Blog
Organic Chem - Education & Industry
Pharma Strategy Blog
No Name No Slogan
Practical Fragments
The Curious Wavefunction
Natural Product Man
Fragment Literature
Chemistry World Blog
Synthetic Nature
Chemistry Blog
Synthesizing Ideas
Eye on FDA
Chemical Forums
Symyx Blog
Sceptical Chymist
Lamentations on Chemistry
Computational Organic Chemistry
Mining Drugs
Henry Rzepa

Science Blogs and News:
Bad Science
The Loom
Uncertain Principles
Fierce Biotech
Blogs for Industry
Omics! Omics!
Young Female Scientist
Notional Slurry
Nobel Intent
SciTech Daily
Science Blog
Gene Expression (I)
Gene Expression (II)
Adventures in Ethics and Science
Transterrestrial Musings
Slashdot Science
Cosmic Variance
Biology News Net

Medical Blogs
DB's Medical Rants
Science-Based Medicine
Respectful Insolence
Diabetes Mine

Economics and Business
Marginal Revolution
The Volokh Conspiracy
Knowledge Problem

Politics / Current Events
Virginia Postrel
Belmont Club
Mickey Kaus

Belles Lettres
Uncouth Reflections
Arts and Letters Daily
In the Pipeline: Don't miss Derek Lowe's excellent commentary on drug discovery and the pharma industry in general at In the Pipeline

In the Pipeline

« ABT-199 Clinical Trial Suspended (Updated) | Main | Pfizer's Covx Closing? »

February 15, 2013

The Finest Blue in the Lab

Email This Entry

Posted by Derek

For Friday afternoon, a bit of chem-geekery. I recently had occasion to use some copper sulfate, and the bottle I had was marked "large crystals" of the pentahydrate. I have loved the color of that stuff since I was a kid, and still do. Powdered, you lose a lot of the effect, but the chunks of crystalline stuff are the very definition of blue. (Photo from egeorge96 on Flickr).

Does anyone know a better one? That's my candidate for the solid phase. In solution, the complex of copper II and pyridine is a good one, a bit more towards royal blue/purple. You can definitely see the change when the pyridine hits it. I can't find a photo of that one on the web; if anyone has one, I'll be glad to post it. More colors to come on other slow Friday afternoons.

Update: a rare gas-phase blue (!) from the comments. Never seen that before!

And another one from the comments: here's someone who really, really, really likes copper sulfate. Here's how it was done.

Comments (42) + TrackBacks (0) | Category: Life in the Drug Labs


1. Scarodactyl on February 15, 2013 12:28 PM writes...

As a trace impurity in tourmaline, copper can produce an incredibly intense windex/pool water blue. Not strictly relevant, but an (alas very expensive) option for getting that vivid copper blue in less soluable form

Permalink to Comment

2. David Borhani on February 15, 2013 12:36 PM writes...

Liquid OK? Nitroso-t-butane. Beautiful, deeeeep blue.

Permalink to Comment

3. Hap on February 15, 2013 12:39 PM writes...

The hexaamine complex of copper(II) is really deep blue, I think (Milkshake referred to it before from a plant making copper sulfate when the workers didn't want to urinate in the cold during the winter). I haven't seen it personally, but chromium(II) should be deep blue, as well, though not air-stable.(Apparently that's only in solution - Wikipedia says CrCl2 is white in the solid state and only blue in solution - ?) Azulene isn't readily available, and it's a darker, less brilliant blue, but it's still pretty.

Permalink to Comment

4. Dave on February 15, 2013 12:52 PM writes...

For those with powdered Copper Sulfate, one option is to recrystallize it. It takes a bit of time, and crystallization is more of an art than a science, but I've done it before, and produced some large, vivid blue crystals.


Permalink to Comment

5. ScientistSailor on February 15, 2013 1:19 PM writes...

You can get a very nice blue color if you let your ozone bubble too long...we called it JOC blue.

Permalink to Comment

6. opsomath on February 15, 2013 1:23 PM writes...

So what were you doing with the CuSO4? I believe I once used the dehydrated, powdered stuff to render 1-hydroxy-1-ferrocenylethane into vinylferrocene. Only time I used it in the lab.

Permalink to Comment

7. Liberal Arts Chemist on February 15, 2013 1:35 PM writes...

Gas phase blue: 3,4-bis(trifluoromethyl)-1,3,2-dithiazolyl

I love Homebrew's comment "Tenure Purple" indeed.

Permalink to Comment

8. Anonymous on February 15, 2013 2:03 PM writes...

How would one recrystallize a solution of copper sulfate to get the largest crystals? I assume it would have to be tightly controlled in terms of temperature and pressure, and would probably take a while, but that would be a great hunk of crystal to have around.

Permalink to Comment

9. andre on February 15, 2013 2:10 PM writes...

I would have thought that azulene would be the chemical that was the very definition of blue (organic and named for its blueness).

Also, I always like solutions of ferrocenium salts. At the right concentrations they can be quite breathtaking.

Permalink to Comment

10. johnnyboy on February 15, 2013 2:13 PM writes...

This is going out of the lab quite a bit, but one of the most mesmerizing works of art i've ever seen is Yves Klein's Victory of Samothrace, rendered entirely in ultramarine pigment, within polyvinyl acetate resin. You can see an amateur photo here:
though images don't do justice to the hallucinatory intensity of the blue.

Permalink to Comment

11. andre on February 15, 2013 2:16 PM writes...

Also, how can you discuss copper sulfate without linking to this?

Permalink to Comment

12. Biotechtranslated on February 15, 2013 2:19 PM writes...

I would have to agree with comment #4.

Cooper sulfate crystals are a very pretty color, but if you dissolve a little up in water and then add a few drops of ammonia you get an incredibly rich and deep blue color.

I use to keep a vial of it on my bench to look at when I missed seeing sunshine.

Permalink to Comment

13. Pig Farmer on February 15, 2013 3:34 PM writes...

@7: that blue gas is pretty damned awesome!
I'm reading a book by Kurt Nassau right now about the physics and chemistry of clour. It's always fascinated me since I grew my first crystals of copper sulfate years ago. Apparently there are 15 different causes of colour.

Permalink to Comment

14. Worm on February 15, 2013 3:49 PM writes...

I don't know if it's the most beautiful, but the sheer chemical, indimidating beauty of the old-school chemical test for (di)chromates, forming chromium (VI) oxide peroxide and extracting it in butanol or (shudder) diethylether has always impressed me more than even the deep royal blue of the cupri-ammonium-complex...

Permalink to Comment

15. Wile E. Coyote, Genius on February 15, 2013 3:54 PM writes...

Cobalt used to make stained glass. See, for example, the stained glass of Chartres Cathedral, aka Chartres blue.

Permalink to Comment

16. Kazoo Chemist on February 15, 2013 4:32 PM writes...

Back in my grad school days I recall several labmates having competitions for growing the largest crystals. Copper sulfate was generally the substrate of choice. You could get a large crystal started and then replenish the mother liquor with a fresh solution to keep the process going.

My personal favorite in the world of large crystals has to be those found in a cave in Mexico. National Geographic has published several stories with remarkable pictures.

Here is just one link:

Permalink to Comment

17. karl on February 15, 2013 4:37 PM writes...


A deeper, more intense blue....

vanadyl sulfate.

Quite stunning.


Permalink to Comment

18. milkshake on February 15, 2013 4:59 PM writes...

If you really want to go full bore, grow purple rhombs of KCr(SO4)2.12 H2O by slow evaporation at room temperature, then finish them in a saturated solution of KAl(SO4)2.12 H2O. Since these salts are fully isomorphic you get a rhombs that have colorless outer layer on the purple crystal seed. You can grow several layers or even do a color gradient, from a mixture of the two salts, in this way. Since desiccation can over time ruin hydrate crystals, you can stabilize your crystal masterpiece by encasing it in a colorless methacrylate "plexiglass" resin

Permalink to Comment

19. JRnonchemist on February 15, 2013 5:38 PM writes...

Clark's Ignition!, IIRC, says that liquid Ozone, and maybe liquid Oxygen, are blue. Anyone know enough about cryogenic photography to point me in the direction of some images? (Of course, there is always the usual issues with color matching and color perception with pictures.)

I remember in gen chem, the professor showed a video of either some orange powder that brunt to green, or a green powder that burnt orange. They said they didn't demonstrate the reaction live anyone more because of carcinogenicity.

I remember that there were some really nicely colored chemicals in gen chem lab. Especially some of the copper hydrates, one of which may well have been the one at top.

Since, I think the color that most made me say 'wow' was the green in some LEDs a year or so back. We had a really nice camera that still did not have the dynamic range to do the LEDs justice.

Permalink to Comment

20. Gordon on February 15, 2013 5:47 PM writes...

Why hasn't anyone mentioned ultramarine yet? Finely ground, it is a pigment with a vivid, vivid blue colour. If you see blue in frescoes or book illuminations, it's likely it's that compound.

Permalink to Comment

21. Kazoo Chemist on February 15, 2013 5:51 PM writes...

The orange to green was ammonium dichromate. It was often used in a model of a volcano, burning out in the open on a bench top. One wonders just how many cancers got started by that demonstration.

Yes, liquid oxygen is blue. It is also paramagnetic. I recall my P-chem prof bringing a dewar of it to class and pouring a blue stream between the poles of a large horseshoe magnet to get a discussion started. A big freakin' explosion would probably have started a quite different discussion.

Permalink to Comment

22. p on February 15, 2013 5:52 PM writes...

Liquid O2 is, indeed, blue. It's also magnetic - a test tube of the stuff loosely hinged and allowed to swing can be displaced with a magnet. It's a cool way to spend an afternoon.

Not recommended at home, though.

Permalink to Comment

23. Rock on February 15, 2013 6:11 PM writes...

The picture you show is lab grown chalcanthite usually from Poland that is sometimes sold to uninformed mineral collectors as naturally occurring.

Permalink to Comment

24. gippgig on February 15, 2013 8:07 PM writes...

Off topic but relevant - Effect of waste drugs in the environment:

Permalink to Comment

25. Sisyphus on February 15, 2013 9:26 PM writes...

@ 24: That rubbish has been floating in the media for the last several years. It is the American Pravda prepping the masses for the govt to take over the Pharma industry via heavy fines and taxation followed by nationalization. Don't believe the hype.

Permalink to Comment

26. Paul on February 15, 2013 9:57 PM writes...

A blue gas is very neat. Has anyone come with an ionic gas (a compound that shows nontrivial ionization in the gas phase at something approaching STP)? How about a superacid gas (where one of those ion species is free protons)?

Permalink to Comment

27. Nick K on February 16, 2013 4:58 AM writes...

How about the gorgeous, infinitely deep blue of the solvated electrons from alkali metals in liquid ammonia? The Birch Reduction is a visual delight.

Permalink to Comment

28. newnickname on February 16, 2013 8:13 AM writes...

@27: "solvated electrons from alkali metals in liquid ammonia? The Birch Reduction is a visual delight."

The post doc who helped me with my first Birch called it The Ty-D-Bol Reaction. ("Ty-D-Bol" = a commercial blue colored toilet disinfectant / cleaner. Search youtube for "ty-d-bol" commercials.)

Permalink to Comment

29. Chris V. on February 17, 2013 12:18 AM writes...

I decided to prep a solution of Cu(II) pyridine from some extra materials laying around.

Here's a photo:

The camera didn't quite do it justice as to the deep blue coloration.

@27: Solutions of polyacetylene have that same gorgeous blue with coppery highlights that birch reductions have. Amazing stuff.

Permalink to Comment

30. Chemystery on February 18, 2013 4:41 AM writes...

Wolfgang Oppolzer's 1-chloro-1-nitrosocyclohexane electrophile is a beautiful blue liquid - even runs on tlc as a blue spot!

Permalink to Comment

31. Cymantrene on February 18, 2013 7:24 AM writes...

Sodium benzofenone can produce nice colors from emerald green through deep blue to purple, depending on solvent and purity.

Permalink to Comment

32. Ben Zene on February 18, 2013 8:39 AM writes...

Try SNAP (CAS 79032-48-7). Crystals appear purple when viewed along one plane. And green when rotated through 90 degrees.

Permalink to Comment

33. SuperScienceGrl on February 18, 2013 12:26 PM writes...

Next time I do a CuSO4/pyridine workup, I'll try and remember to snap a pic and show you!

Permalink to Comment

34. Flatland on February 18, 2013 1:26 PM writes...

The various 6,13-pentacene derivatives get my vote for blue (the crystals are a really nice blue/black shade), and bonus points for usually glowing red when excited.

I also have to agree also with the Cu(I)/(II) chemistry. Glaser/Eglinton/Hay couplings were always especially pleasing to my eye.

Permalink to Comment

35. Xmas on February 18, 2013 6:42 PM writes...

It's not chemistry, but I did enjoy seeing the blue Cherenkov radiation during my nuclear physics lab. WPI has (had?) an open pool nuclear reactor, and you could see the blue glow from the block at the bottom.

Permalink to Comment

36. JJBP on February 19, 2013 8:59 AM writes...

Azulene! Like in this mushroom...

Permalink to Comment

37. Robert Bruce Thompson on February 19, 2013 2:03 PM writes...

Big copper sulfate crystals are gorgeous, and I love the blue the solution provides with ammonia as a ligand, but my favorite Lab Blue has to be the transformation from a brownish-green sludge to a beautiful intense clear blue when making up biuret reagent. I wrote about it here:

Permalink to Comment

38. Kent G. Budge on February 20, 2013 11:07 AM writes...

Did anyone else ever have a Mr. Wizard crystal growing kit as a kid? Copper sulfate was one of the feedstocks supplied in quantity with the kit. It turns out growing large copper sulfate crystals is easy enough for a bright 10-year-old to do.

It turns out the crystals are triclinic; they have essentially no symmetry whatsoever. If you want symmetry, potassium alum doped with a small amount of chrome alum is your ticket. You get octahedrons. Purple rather than blue, though.

Permalink to Comment

39. Timo on February 21, 2013 6:39 AM writes...

My favourite liquid blue is a solution of C-phycocyanin. Not too spectacular as a solid, though...

Permalink to Comment

40. joeylawn on February 21, 2013 11:54 PM writes...

Indium Gallium Nitride in a semiconductor diode....Blue LED's. ;)

Permalink to Comment

41. ChristianPFC on March 5, 2013 4:14 AM writes...

I think copper sulfate and vanadyl sulfate look very similar, I might be unable to distinguish them.

Sodium-Benzophenone and sodium in ammonia are too dark blue for my taste, but during the preparation there is a concentration where it is just right.

Long time ago, I prepared Cr(OtBu)4 (following a patent, from CrCl3 and NaOtBu in THF, I don't know where the redox took place), which was a deep blue liquid (distilled, yield was low and some impurities in NMR and EA).

Permalink to Comment

42. Robert Leponge on March 8, 2013 3:01 PM writes...

Copper Sulfate reminds me this installation from Roger Hiorns:

Permalink to Comment


Remember Me?


Email this entry to:

Your email address:

Message (optional):

The Last Post
The GSK Layoffs Continue, By Proxy
The Move is Nigh
Another Alzheimer's IPO
Cutbacks at C&E News
Sanofi Pays to Get Back Into Oncology
An Irresponsible Statement About Curing Cancer
Oliver Sacks on Turning Back to Chemistry