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In the spring of 2019, Dr. Melissa Tedone, of the Winterthur Museum in Delaware, lent out an old book published in 1857 from the library. It is a home decoration guide, the book is called "Rural Decoration-for tasteful Home" (Rustic adornments for homes of taste).

The book is beautiful, and although it has been for more than a century, it still has a bright green appearance, which matches the gilded fonts and patterns. As one of the collections to be displayed at the Winterthur Museum of Art, even though the spine and coat are about to fall off and the seams are broken, its eye-catching colors are still impressive.

Dr. Tedden's task is to repair the book before the exhibition opens. Under the microscope, she saw a black wax attached to her book coat and tried to brush it off gently with a soft porcupine quill, only to find thin shavings falling off where the bristles passed. This may come as no surprise to others, but Dr. Tedden was so surprised that she began to suspect that the coat was painted with pigment instead of dye.

Pigments and dyes are colorants, but dyes are usually soluble, while pigments are insoluble and will be suspended in the liquid in the form of particles. If the book coat is colored with paint, it is not difficult to explain why the cohesion of the coating is not strong, even the softest touch from the quill is enough to take away a touch of color.

But when it comes to pigments, especially green pigments, Dr. Tedden can't help remembering that the book was born in the 19th century, when some bright and poisonous green pigments were the most popular. This made her worry about whether she, who met the old Green Paper more than 100 years later, was still poisoned by the previous "fashion trend".

Green is so healthy, how can it be poisonous? Green is probably the most indispensable color in nature. However, it is not easy to turn this ubiquitous green directly into pigments or dyes for human use. The green people extract from plants is often very unstable, at first it is green, and soon it will turn a dull brown.

It is difficult to collect stable green from plant components, so human beings are bound to pay more attention to minerals. For example, the ancient Egyptians mined malachite and grinded it as a green pigment and used it in some paintings of the tomb walls of the pharaohs, dating back to the fourth dynasty (2613-2494 BC). During the Renaissance, there were still many artists painting with malachite paint. The main component of malachite is basic copper carbonate, which can retain the original color for a long time in oil painting and tempera painting.

Sistine Notre Dame of Raphael uses malachite paint (Photo: Wikimedia Commons) since malachite, many copper-containing pigments have left their own green at different times in history. However, most of them may not be as famous as Scheele's Green, which was born in 1775.

In 1775, a chemist named Karl Scheele slowly added arsenic trioxide (commonly known as arsenic) to heated sodium carbonate solution to obtain sodium arsenite, and then poured sodium arsenite solution into copper sulfate solution to obtain copper arsenite precipitation. This is Scheler green, its color is bright and not easy to fade, and low production cost, soon became a star product on the market, leaving other green pigments in the cold.

The painting "the woman who makes embroidery" uses Scheler Green (photo source: Wikimedia Commons). This pigment is not only active on the artist's canvas, but also begins to enter every corner of human life. The wallpaper at home, the clothes on the body, and the children's toys have all become the objects of Scheler green coloring. Sometimes it is added to candy as a food pigment. Although arsenic trioxide was used as a poison in the Middle Ages, there was no widespread understanding of the toxicity of arsenic compounds in the 19th century.

When people find that Scheler green turns black when it comes to sulfides, they even want to create more durable green pigments on that basis. In 1814, two German chemists improved Scheler's formula, using arsenic trioxide and copper acetate to obtain copper arsenite acetate precipitation, also known as "emerald green". After the birth of this bright new paint, along the road of Schelelu, it was loved by many painters and invaded the lives of ordinary people on a large scale. Later, it also had a louder name-"Paris Green" (Paris Green).

The left uses Paris green wallpaper, and the right uses Paris green Van Gogh's self-portrait (photo source: Wikimedia Commons) Scheler Green and Paris Green, both of which led the Victorian color trend. While these arsenic-containing pigments are popular, there are more and more poisoning incidents related to them.

The people who have the most daily exposure to these pigments are probably the workers who are responsible for coloring the goods. In 1861, a 19-year-old girl died in a factory in London, coloring artificial flowers with green powder containing arsenic. At the end of her life, her fingernails and whites of her eyes were green. An autopsy found arsenic in her stomach as well as in her liver and lungs.

When arsenic-rich goods come out of the factory, consumers may be the next victim of arsenic. In London in 1862, in a family surnamed Turner, parents lost three children in succession, and a living daughter was seriously ill. Originally, according to the symptoms, doctors thought that children had diphtheria, a respiratory infectious disease that was very common at that time. But oddly enough, the other people who had frequent contact with the children did not catch the same disease. In addition, the Turner family and the community have good drainage and ventilation, and no serious health risks have been found. Finally, the doctor suspected the green wallpaper in the patient's house.

Soon after, the seriously ill child also died. After testing her tissue samples, some chemists believe that arsenic poisoning may be the real cause of death.

Since then, many similar events have led people to believe that green pigments containing arsenic are harmful, and that even if people do not touch them, the particles that fall off will float into the air, and if inhaled in large quantities by humans, it may cause physical discomfort, such as dizziness or diarrhea. Moreover, children and the elderly may be more vulnerable than healthy adults if they are exposed to arsenic for a long time.

Later, Scheler Green and Paris Green were gradually abandoned. Nowadays, it should be difficult to find these two kinds of paint in whose green wallpaper. However, some items left over from the Victorian era may still be the same color or toxic. For example, the book mentioned at the beginning.

In Project Poison, Dr. Melissa Tedden will be suspicious of a 19th-century book, not least because she easily scraped green crumbs off her coat. In addition, she remembered that she had seen Victorian green wallpaper patterns in a book published in recent years, which was very similar to the color of the old book coat she was repairing.

Dr. Teddon boldly guessed that the paint used on the book coat was Paris green. To confirm her suspicions, she turned to Rosie Grayburn, a researcher who also works at the Winterthur Museum. Grayburn first analyzed the elements in the green book coat by X-ray fluorescence spectrometry (XRF) and found that copper and arsenic were present and the content was not low.

Use XRF to analyze 19th-century books (photo source: Winterthur Museum) but XRF can only determine the elemental composition of the samples, and what molecules those elements make up together need to be further determined. Grayburn uses Raman spectroscopy to study molecular structure, and when a laser hits each molecule, it gets a unique scattering spectrum, like a unique "fingerprint", that distinguishes it from other molecules. This method allowed scientists to confirm that the pigment on the surface of the book was copper arsenite acetate-Paris Green.

Although his idea was confirmed, Dr. Tedden was shocked: "I knew there would be arsenic paint in the wallpaper in the past, and I also knew that arsenic paint would be used in some of the illustrations in books, but I didn't expect this poisonous thing to cover the cover." you will encounter it when you read the book in your hand. "

Not only that, Teddon and Grayborn also found that the book coat contained 1.42 milligrams of arsenic per square centimeter. If left untreated, the lethal dose of arsenic poisoning in adults is 100 mg. Dr. Tedden believes that he only made some simple treatment of the book, which may not cause significant harm, but if he is a library staff, he will face greater risk if he has more exposure to arsenic paint.

Long-term exposure to inorganic arsenic may cause many health problems, such as skin damage, peripheral neuropathy and so on. Some cardiovascular diseases, respiratory diseases, liver diseases and even cancers in some organs are also related to inorganic arsenic.

As a result, the two researchers decided to launch the poison book project, hoping to find and catalogue more books from the 19th century that could be harmful to the human body. In the Winterthur library alone, they detected nine "toxic" collections, four of which were circulated between different libraries. At the Philadelphia Library Company (Library Company of Philadelphia), the oldest library in the United States, they found 28 old books containing Paris Green.

Books with Paris Green on the cover (photo source: Winterthur Museum) so far, Teiden and Grayborn have found 92 books with Paris Green on their covers. They also distribute "colorimetric" bookmarks around to help people identify which colors are more like 19th-century Paris green. Whenever suspicious objects are found, the researchers use XRF to detect elements as they did at first, and if suspicious elements are found, Raman spectra are used to further confirm them.

Of course, identifying toxic books is only a step in the plan, and more importantly, to reduce the harm those books do to people. Greyborn says arsenic can be dangerous if it seeps into the skin of the hand, especially if it is eaten from the mouth or through the respiratory tract. The poison book project lists some precautions for people who need to be exposed to poison books:

Wear nitrile gloves and N95 mask before operation. During operation, avoid eating, drinking and smoking, do not let the material on your hands touch your face; wash your hands after operation. In addition, do not operate on a soft surface (such as a sofa), you should put the poison book on the hard surface such as the table, and wipe the surface of the book with a wet cloth after the operation to remove the residual toxic particles.

Photo Source: Melissa Tedone & Rosie Grayburn, of course, a luckier and more convenient situation is never to encounter these poisonous books. Although most libraries with collections of books in the mid-19th century have a few bright green books, it may be difficult for ordinary people to come across. In addition, not every green book from the 19th century is colored with arsenic pigments.

Dr. Teddon also said: "I happened to meet that one, that's all."

Original paper:

Https://www.tandfonline.com/doi/abs/10.1080/01971360.2022.2031457

Reference:

Https://www.udel.edu/udaily/2022/june/poison-books-arsenic-bindings-covers-pigments-dyes/

Https://www.iiconservation.org/content/poison-book-project

Https://www.nationalgeographic.com/science/article/these-green-books-are-literally-poisonous

Http://wiki.winterthur.org/wiki/Poison_Book_Project

Https://www.finebooksmagazine.com/issue/conservators-find-arsenic-old-books

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by: chestnut revision: clefable

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