Chemical Heritage Foundation

The people of the Chemical Heritage Foundation are stewards of the objects, ideas and stories that chronicle humanity's drive to understand the material world through experimentation. If you connect to our passion for sharing this legacy, we hope you'll add your perspective to the content here and pass it along to your online communities.


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    The Summer Issue of Chemical Heritage Magazine is Here

    Chemical Heritage magazine has escaped from captivity yet again. This time it has crime in mind. If you have an appetite for detective stories or obscure poisons you’ll find much to chew on.  If you’re worried about the increasingly rude conversations around scientific “controversies,” well, keep worrying. (There aren’t any simple answers.) If you want more to worry about, check out the history of Atoms for Peace or find out why depression diagnoses keep growing .  Finish up with something more cheerful, such as oursous vide story (though even that has a sting in its tail).

    Check out the entire online summer issue here.

    Sign up for a free trial subscription to the print magazine here.

    Image: Portrait of Dorothy Sayers, progenitor of forensic-based crime fiction. A portrait of Sayers also appears on the cover of the summer magazine. (National Portrait Gallery, London)

    Blue Blood Donors


    In the first half of the 20th century, scientists faced a vexing  problem. Too many people were being sickened and killed by bacterial endotoxin—a substance in a bacteria’s outer membrane toxic to animals and resistant to heat—contracted through vaccines and surgery tools. The only way to determine if something was contaminated was to test it on animals, a slow and expensive process.

    In 1956 a scientist named Fred Bang was studying the blood circulation in horseshoe crabs. He observed that when a crab became infected with gram-negative bacteria (a type of bacteria difficult to detect with standard tests), its blood coagulated and turned into a thick jelly.  He continued analyzing this phenomenon and found that horseshoe crab blood contains a cell that releases a clotting agent that captures foreign contaminants before they infect the whole crab.

    Horseshoe crabs need this clotting ability to keep the billions of microscopic organisms in the ocean at bay. If a crab gets a cut or a puncture in its shell, its blood will harden around the hole and freeze foreign contaminants in place. This trait may have helped the horseshoe become one of the oldest living animals; the species is more than 500 million years old.

    Scientists were quick to isolate the clotting agent (named Limulus amebocyte lysate, or LAL) and use it to test the presence of bacteria in medicine and pharmaceutical equipment. If the LAL turns into gel after coming into contact with a vaccine, the vaccine is contaminated. If nothing happens, it is safe to use on humans. This simple test has saved thousands of lives since its invention.

    The only issue is that scientists now need horseshoe crab blood, and lots of it. Hundreds of thousands of crabs are bled each year to keep up with the demand for LAL, and each time a crab is harvested about 30% of its blood is taken before it is released back into the ocean. The blood is drained by strapping down the crab and inserting a large needle into the tissue near its heart. The medical industry claims that mortality rates are low, but some studies suggest that as many as 15% of all crabs harvested end up dying.  Additionally, other studies have shown that even though the crabs can replenish most of their blood in a few weeks, the harvesting process has a detrimental effect on their movement speed and breeding ability. With horseshoe crab populations already threatened by fishermen who use them as bait, pharmaceutical companies need to switch to an alternative to LAL sooner rather than later.

    Luckily there are some promising substitutes already available. A laboratory at Princeton University is testing microchip coated with antimicrobial peptides found on the back of the African clawed frog. When the peptides react with bacteria, the microchip sends out an alert. Other labs have developed recombinant Factor C, essentially a synthetic version of the clotting agent in horseshoe crab blood.

    By Jacob Roberts

    Image: Horseshoe crab blood is harvested and used to test for vaccines for potentially deadly contaminations. The bright blue color of the animal’s blood comes from the copper molecules used to carry oxygen (human blood uses iron). Wikimedia Commons.

    The End of Beer


    It’s last call for our beer theme. And this 1908 postcard from our collections seems a good nightcap.

    If you’re still thirsty, we have some top-shelf options for you:

    Our recent beer podcast

    Our recent beer webcast

    Old beer podcast on beer and brewing with another visit to Dogfish Head Brewery

    What the heck, how about a final image from our collection - a brewing book with a long title, published in 1692.


    (Top image from the Donald F. Othmer Papers, CHF Archives, Album Gravures et Cartes-Postales: Vieux Paris Types Petites Métiers et Cris De La Rue (1908). Bottom image from the Roy G. Neville Historical Chemical Library, Othmer Library.)

    Intoxication & Civilization: The Podcast

    This episode of Distillations of takes on the frothy subject of beer, and explores the science, culture, and history behind the suds.

    "Intoxication and Civilization: Beer’s Ancient Past" features beer and wine archaeologist Patrick E. McGovern and chemist, professor, and home brewer Roger Barth.

    Our guests discuss the science behind beer, how modern craft breweries can help us understand ancient beers, and how technology has allowed us to drink like an ancient king. They also discuss the spiritual side of beer and the role beer has played in human evolution.

    But first, Bob and Michal go back to school—beer school. Take a listen.

    Of Beer and Genes


    I have a low tolerance for alcohol, which became embarrassingly public on our recent beer webcast. My co-host, Bob, and I were drinking with beer archaeologist Pat McGovern and chemist and home brewer Roger Barth.

    There was lots of history, culture, and science on the show, as well as actual beer. I found the conversation fascinating, and we didn’t get to talk about half the things we wanted to. But there is one moment that will stick in my memory. I had drunk half my bottle, (the others were on to their second bottle), when I almost knocked over something on the table with my beer glass and said something like, “Oops, looks like I’ve already had too much.”

    After the show (and after I’d recovered from embarrassment) I got to thinking. On the show Pat had spoken about the flush reaction many ethnically Asian people suffer from after drinking alcohol—nausea, flushing of the face, pounding heart—which is caused by a mutation in an enzyme that metabolizes acetaldehyde, which is itself a byproduct of the metabolism of alcohol. When acetaldehyde builds up in the body, the symptoms appear.

    I’m not Asian, but I do get the flushing and the nausea, which is why I drink so little (and the reason why my alcohol tolerance is so low). I went searching online and found an NIH webpage that discusses the gene variants, or alleles, involved in this response. On the bright side, some of these variants result in a significantly reduced risk for alcoholism. (Who wants to drink when acetaldehyde produces such nasty side effects?) It turns out that non-Asians also carry some of these variants. In fact, the NIH page includes this nugget: “Among people of Jewish descent, the ADH1B* allele is found at moderate frequencies and reduces binge drinking … and risk for alcoholism.”  

    So, I may have found an answer to my (lack of a) drinking problem. Of course without genetic testing I don’t know for sure whether I have a gene variant that affects how my body metabolizes alcohol and/or acetaldehyde. But I do now think that moment of embarrassment (which a friend described as a lovely moment of candor) was worth it; it led me to a fascinating intersection of health, culture, genes, and behavior.

    The podcast of that show is now online (with a few judicious cuts) and it includes a visit to beer school, where Bob and I learned more about the different ingredients that end up in beers.

    By Michal Meyer

    (Image: Solid Comfort, 1906. A man enjoys a cigar and a beer. Library of Congress.)

    A Feast for Mosquitoes


    We’ve been writing a lot about mosquitoes lately in Chemical Heritage magazine, so blood suckers were on my mind when I was riding a Washington, D.C. Metro train a few weeks ago and noticed a strange advertisement. A poster requested participants in a study to test a potential malaria vaccine delivered by mosquitoes. If you don’t mind letting a malaria-ridden mosquito feast on your blood, you could be paid to be a test subject. Normally mosquitoes are the carriers of malaria, so I was surprised to see them being tested as flying, vaccine-filled syringes.

    Scientists have not yet invented a vaccine for malaria, but current efforts involve introducing a weakened version of the organism that causes the disease into the human body. In response the immune system has time to set up defenses that will deal with stronger malaria parasites trying to enter the body in the future. In this study scientists made the deadliest strain of malaria harmless by deleting certain genes. In another study the undeveloped larvae was weakened with radiation.

    Delivering malaria vaccines on a large scale by releasing mosquitoes into the wild would be revolutionary. No longer would people living in rural areas have to seek out doctors and nurses to find medication; the vaccinated mosquitoes would find them instead. Scientists are a long way off from taking these mosquitoes out of the lab. And of course, there are ethical considerations: it would be next to impossible for people to opt out of vaccination on such a large scale. Still, humanity has been through similar ethical dilemmas before, such as with the fluoridation of the public water supply in the United States.

    What do you think? Are mosquito-delivered vaccines practical or even possible? And if they are, should we be using them? Let us know in the comments section below.

    By Jacob Roberts

    Image: Aedes aegypti biting a human. Wikimedia Commons.

    Remembering Stephanie Kwolek, Inventor of Kevlar

    It’s not every day that a woman invents a life-saving fabric. Chemist Stephanie Kwolek, who died Wednesday at age 90, invented Kevlar, a material both stronger and lighter than steel. Today Kevlar is used when lightweight strength is required, whether it’s bicycle tires, bulletproof vests, or protecting undersea fiber-optic cables.  Even more impressive, Kwolek made her discovery in the 1960s, a time when science was not especially welcoming to women.

    Kwolek loved fabrics and fashions and initially planned to be a fashion designer. She eventually settled on chemistry and worked for DuPont her whole career. By some standards she might be considered a late bloomer; not until her 40s did she discover Kevlar. In some ways her work brought her full circle: the frustrated fashion designer helped create life-saving fabrics worn by people all over the world.

    For more on Kwolek’s life and work, follow these links:

    Basic history

    Kwolek’s CHF oral history

    By Michal Meyer

    Beer and Brewing Podcast


    In honor of this month’s webcast theme, we dug up a Distillations podcast from 2008: "Beer and Brewing." It turns out that CHF has been to the Dogfish Head brewery once before. Tune in to learn about fermentation, ancient brews, and how alpha acids affect the bitterness of beer.

    Image: Detail of a hops plant in the hops fields near Olomouc. The photo was uploaded by nutto to stock.xchange.

    Philly Beer Week


    Beer Week is winding down in Philadelphia. Self described as “the largest beer celebration of its kind in America,” the festival features such events as this beer garden at the Shambles at Headhouse Square and the tapping of rare and unusual brews at bars and restaurants all over the city.

    Want to know more about the science and history behind beer making? Check out the latest Distillations webcast: “Intoxication and Civilization.

    Tell us about your experiments with the science of brewing in the comments.

    Read more

    A Day at Dogfish Head Brewery


    In late April I was lucky enough to join my teammates on a trip to film the Dogfish Head brewery. Ostensibly I was there to take pictures and write about the trip, but I suspect the real reason I was invited was to drive everyone home in case the beer proved to be too delicious.

    Located in Milton, Delaware, and nestled between cornfields and the beach, it’s easy to see why Dogfish Head’s founder, Sam Calagione, chose this spot for his company. Before Dogfish Head set up shop in 1995, Delaware was one of only a handful of states without a brew pub. The state actually had to change Prohibition-era laws to allow Dogfish Head to operate.

    While growing, Dogfish Head is still a tiny operation when compared to the makers of Budweiser and Miller. It’s what’s called a craft brewery, and often part of being a craft brewery is making unusual beers. Dogfish Head makes some particularly strange brews. Calagione once created a brew called Chicha, based on traditional Peruvian beer made with corn. Just as ancient Peruvians once did (and still do), Dogfish Head brewers chewed the corn in their own mouths to convert the starches into sugar. I turns out enzymes in human saliva are almost as effective at transforming starch into sugar as the traditional germination process is.

    But the beers we were most interested in were their ancient ales, brews made with recipes based on the analysis of residue found in pottery at archeological sites. Pat McGovern, or Dr. Pat as he known to the folks at Dogfish Head (and a guest on our May webcast), is a “beer archaeologist” whose research has inspired many brews. One of Dogfish Head’s most popular ancient ales is called Midas Touch, made from honey, grapes, and saffron. It was Dr. Pat’s first collaboration with Dogfish Head, one in which he used molecular analysis on pottery found in the tomb of King Midas in Turkey to determine the ingredients.

    The oldest recipe brewed so far at Dogfish Head is from Jiahu, a 9,000-year-old Neolithic village in China. Named Chateau Jiahu, the beer is made from rice, honey, fruit, and flowers. The brewery claims that the beer is based on the oldest-known fermented beverage in the world. Reading the list of ancient ales is like looking at a timeline of the history of beer making.

    Dogfish Head is one of the first American breweries to use materials besides metal to store their aging beer. Oak and terra cotta allow oxygen to permeate the beer and “soften” it, say the people at Dogfish Head. The process releases some of the alcohol into the air, and you smell it immediately. One vat is made from Palo Santo (“holy tree”), an incredibly dense type of wood from South America that imparts a slight spiciness to the beer. The wood is so dense that when I tried picking up a small slab of it, it felt like a heavy stone.

    There were many other things I learned during the shoot, far more than I can fit here. If you want to know more about the chemistry of beer, watch the webcast on CHF’s Tumblr and check out pictures from the trip on Flickr.

    By Jacob Roberts

    Image: The CHF crew records Justin Williams, Off-Centered Storyteller at Dogfish Head, as he explains the beer aging process. On the far left is a vat made of Palo Santo.

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