Pain perdu - a delicious part of my New Orleans heritage and better known in most of the US as french toast - has a long history. The earliest extant recipe is in Latin and dates to the 4th or 5th century! Friday brought a snow day for my kids, and come evening, some experimental time for me in my favorite home lab.
After a day spent teaching and shoveling in the sleet, I made pain perdu aux pommes from Simon Hopkinson's Second Helpings of Roast Chicken. Think french toast, vanilla custard, apples and caramel sauce. The first step in making the caramel sauce is to melt sugar over high heat. As I stirred the dry sugar in my heaviest sauce pot, alert for the first sign of melting, I flashed back to my days in an organic chemistry research lab. Melting points were used both to identify products (though even then, spectroscopic methods such as NMR were the gold standard) and to verify purity. Taking an accurate melting point required patience - and being attentive to the appearance of that first glistening drop of liquid in the fine capillary tube. It looked almost as if the crystals were sweating.
How is the purity of a compound related to its melting point? An impure sample will tend to melt over a few degree range, pure samples will melt at a sharp temperature. Impurities in a solid will also depress its melting point, in the same way that applying salt to ice (another application of chemistry appropriate for a snow day) lowers the freezing point. This phenomena also offers a low tech way to confirm the identity of a compound. Make a mixture of the sample to be identified and a known sample of (presumably) the same stuff. If the melting point is sharp and the same as the pure compound, the unknown is certain to be what you think it is. This will work even if the melting points of the two compounds are fortuitously the same.
A nice film of a melting in a capillary tube can be found at Wellesley's organic chem lab site.
- Home
- Angry by Choice
- Catalogue of Organisms
- Chinleana
- Doc Madhattan
- Games with Words
- Genomics, Medicine, and Pseudoscience
- History of Geology
- Moss Plants and More
- Pleiotropy
- Plektix
- RRResearch
- Skeptic Wonder
- The Culture of Chemistry
- The Curious Wavefunction
- The Phytophactor
- The View from a Microbiologist
- Variety of Life
Field of Science
-
-
From Valley Forge to the Lab: Parallels between Washington's Maneuvers and Drug Development3 weeks ago in The Curious Wavefunction
-
Political pollsters are pretending they know what's happening. They don't.3 weeks ago in Genomics, Medicine, and Pseudoscience
-
-
Course Corrections5 months ago in Angry by Choice
-
-
The Site is Dead, Long Live the Site2 years ago in Catalogue of Organisms
-
The Site is Dead, Long Live the Site2 years ago in Variety of Life
-
Does mathematics carry human biases?4 years ago in PLEKTIX
-
-
-
-
A New Placodont from the Late Triassic of China5 years ago in Chinleana
-
Posted: July 22, 2018 at 03:03PM6 years ago in Field Notes
-
Bryophyte Herbarium Survey7 years ago in Moss Plants and More
-
Harnessing innate immunity to cure HIV8 years ago in Rule of 6ix
-
WE MOVED!8 years ago in Games with Words
-
-
-
-
post doc job opportunity on ribosome biochemistry!9 years ago in Protein Evolution and Other Musings
-
Growing the kidney: re-blogged from Science Bitez9 years ago in The View from a Microbiologist
-
Blogging Microbes- Communicating Microbiology to Netizens10 years ago in Memoirs of a Defective Brain
-
-
-
The Lure of the Obscure? Guest Post by Frank Stahl12 years ago in Sex, Genes & Evolution
-
-
Lab Rat Moving House13 years ago in Life of a Lab Rat
-
Goodbye FoS, thanks for all the laughs13 years ago in Disease Prone
-
-
Slideshow of NASA's Stardust-NExT Mission Comet Tempel 1 Flyby13 years ago in The Large Picture Blog
-
in The Biology Files
The Who, What, When, Where and Why of Chemistry
Chemistry is not a world unto itself. It is woven firmly into the fabric of the rest of the world, and various fields, from literature to archeology, thread their way through the chemist's text.
Repackaging Vitamins: Niacin
Vitamins are small molecules (where small is relative to proteins!) that a living organism cannot synthesize, but are nevertheless required. The word vitamin was coined by a Polish biochemist, Kazimierz Funk by sandwiching together "vital" and "amine". Not all vitamins turned out to be amines (molecules with an NH2 group in them), however the name stuck.
One such non-amine "vital amine" has the structure shown below. It's a carboxylic acid (the COOH group). Originally designated as vitamin PP, it is now better known as the third of the B vitamin complex or B3. PP stood for pellagra preventing factor. Pellagra is a nutritional deficiency, once common in Italy, that results in rough skin - pella is Italian for skin.
The original common chemical name for B3 was nicotinic acid. (The synthetic form can be made by oxidizing nicotine with nitric acid.) In the late 1930s, niacin (NIcotinic ACid vitamIN) was adopted as the preferred name, to avoid confusion with nicotine. (I'm unclear why this was undesirable; smoking was pervasive.)
Repackaging scientific terms to make them less frightening for the general public is not just a historical phenomenon. Much more recently the application of NMR (nuclear magnet resonance) to medical imaging saw its "nuclear" dropped (thus forestalling any potential association with nuclear radiation) to become MRI (magnetic resonance imaging). It should be made clear, that like nicotinic acid, which contains no nicotine, NMR does not require nuclear radiation.
Ant-acids
I'm teaching general chemistry this semester. Acids and bases are currently on our agenda, in particular how to assess the strength of an acid based on its molecular structure. When dissolved in water, strong acids, such as hydrochloric acid (HCl) or sulfuric acid (H2SO4) always transfer their protons (H) to water. For example: HCl + H2O → Cl– + H3O+. Weak acids result when only some acid molecules transfer their protons to water. Organic acids, containing only carbon, oxygen, hydrogen and nitrogen, are generally weak acids. The archetypical weak organic acid is acetic acid, better known as vinegar: CH3COOH. It's not the simplest organic acid, that would be formic acid: HCOOH.
Formic acid was first characterized in the late 17th century. Naturalists had observed that the vapors emitted by ant hills were acidic (using the equivalent of litmus paper), and in 1671 John Ray extracted the pure acid by distilling the crushed remains of red ants. Formica is Latin for ant, hence the name translates pretty literally as "ant acid". Formic acid is at least partially responsible for the sting in bee stings, ant bites and stinging nettles.
Even though chemists call formic acid weak, a 0.10 M solution has a pH of 2.4 (for comparison's sake, the same concentration of HCl has a pH of 1.0).
I remember find ants all over my Formica counter in my post-doc days. Does the ubiquitous counter-top material have any connection to ants? Apparently not. It was originally created as a substitute for mica insulators. For mica....
Formic acid was first characterized in the late 17th century. Naturalists had observed that the vapors emitted by ant hills were acidic (using the equivalent of litmus paper), and in 1671 John Ray extracted the pure acid by distilling the crushed remains of red ants. Formica is Latin for ant, hence the name translates pretty literally as "ant acid". Formic acid is at least partially responsible for the sting in bee stings, ant bites and stinging nettles.
Even though chemists call formic acid weak, a 0.10 M solution has a pH of 2.4 (for comparison's sake, the same concentration of HCl has a pH of 1.0).
I remember find ants all over my Formica counter in my post-doc days. Does the ubiquitous counter-top material have any connection to ants? Apparently not. It was originally created as a substitute for mica insulators. For mica....
Subscribe to:
Posts (Atom)