THE NAME thallium comes from the Greek word thallos for a newly leafed plant, brilliant with the sun-bright green of spring. It seems a strangely vivid description for a less-than-colorful metallic element, silvery pale in the ground, darkening to tarnished gray when exposed to air.
But the story of its scientific discovery explains the name, as well as the scientific advances entailed in that discovery. Thallium was first identified in 1861 by a leading British chemist. William Crookes had been asked to analyze a batch of sulfuric acid, used in industrial mining, which was apparently tainted with an unknown impurity. Following his usual routine, Crookes started with a simple flame test. He dipped a platinum wire into the acid and put the wire into the colorless fire of a Bunsen burner.
As it heated, the wire lit to a sudden brilliant green.
Crookes had done hundreds of flame tests. He’d seen other elements that flashed green—copper and barium, for example. But the springlike exuberance of this color was new to him. He decided to run a more sophisticated test on a new instrument, the spectroscope. The device worked on the same principle as the flame test: when a material heats to incandescence, it emits light of varying colors according to its atomic makeup. In a spectroscope, an unknown compound was heated until it glowed. The resulting light was directed through a slit and into a prism. The prism then refracted the light into its full spectrum, whatever that might be. A scientist looking at those bright shimmers through a magnifying tube could identify each component of the heated material, matching the color to the existing chemical catalog.
But the clear green line that Crookes saw in the spectroscope was unknown, leading him to realize that he’d found a new element. He named his discovery thallium, for its unique spectroscopic color. As it turned out, Crookes would be forced to share the credit. That same year, a chemist in France, Claude-August Lamy, reported finding surprising green lines of light in tests of mining residues. Lamy had taken the discovery further, isolating the element and casting a small metallic ingot. The French scientist also (although this would be appreciated only much later) provided the first suspicions that thallium was a treacherous material.
During the months that he spent isolating thallium, Lamy’s health progressively faltered. He suffered from a stumbling exhaustion and shooting pains in his legs. He recovered, but he was troubled enough to further test the element by feeding it to dogs, ducks, and chickens. All died in a few days, suffering from weakness, trembling, difficulty breathing, and, in the worst instance, paralysis in their legs.
Crookes greatly resented what he saw as an attempt to steal his discovery, and he refused to accept his rival’s concerns. At high doses thallium might be dangerous, the British chemist acknowledged. But small doses, which he’d tried himself, had no health effects at all.
Crookes edited a leading chemistry journal, so his well-publicized assessment was the one that gained scientific acceptance. It was too bad, of course, that in this particular detail he was wrong.
“FIVE IN FAMILY KILLED by Rare Poison” read the New York Times headline on May 11. The Gross family story rated the newspaper’s front page; after all, how often did a $20-a-week clerk, as the paper put it, murder his own children with an exotically unusual toxic agent?
The deaths had been too many, and too close together, to avoid investigation. The police work started after Gross’s last remaining child, little Frank, and his mother-in-law, Olga Bein, ended up in Brooklyn’s Bushwick Hospital. A local physician, who had just acquired a spectroscope, was sent tissue scrapings taken in the hospital. The tests resulted in an unmistakable evil dazzle of green. The district attorney then had the bodies of Gross’s wife and eldest son exhumed. In those tests as well, the physician saw the lethal green signature of thallium.
The police questioned Gross for twenty-eight frustrating hours, trying to get him to confess to the murders. He maintained his innocence and bewilderment—he could not understand how thallium had been found in the bodies of his family. By the time he was sent to his jail cell, he sat down on the cot and fell straight asleep, still dressed in his one good suit.
THALLIUM was surprisingly easy to obtain, despite what Alexander Gettler described as “its relatively rare occurrence and high cost.” Beyond its cosmetic uses, it had been incorporated into a wide array of industrial products.
Thallium served to strengthen the filaments in tungsten lamps. When metallic thallium was melded into glass, it strengthened light refraction, making it valuable in manufacturing eyeglass lenses and in giving sparkle to artificial gemstones. Added to the mercury alloy used in thermometers, thallium helped achieve accuracy down to minus 60 degrees centigrade.
Concentrated doses of thallium salts were used in pest control; it had been mixed into rodent poisons since 1920, sold as Zelio paste and Thalrat. It was the toxic ingredient in a pest-killing bait marketed as Thalgrain. In the early twentieth century it had been used to remove the hair of children with scalp infections, such as ringworm, so that doctors could see and treat the fungus. But that practice had been abandoned when too many of the toddlers died.
AS THE U.S. Public Health Service noted in a review of thallium’s use in medicine, every animal tested—mice, rats, guinea pigs, dogs, rabbits, and apes—lost its hair or fur when taking a daily dose of thallium.
Researchers were unsure exactly why. That thallium was the only metallic poison to cause loss of hair seemed peculiar, but animal research suggested that it was related to an unusually rapid destruction of skin cells. Later studies would find that one reason thallium caused such accelerated damage was that it possesses an atomic structure very like another soft metal, potassium. In the same way that radium takes advantage of the body’s natural affinity for calcium, thallium tends to move rapidly along potassium-uptake channels into the nuclei of cells.
But where potassium helps maintain a proper fluid balance in cell walls and feeds the nerve cells that control muscle movement, thallium disrupts cell metabolism and splinters apart chemical bonds. The potassium channels too provided a depressingly efficient way to spread the poison’s effects. “Animals poisoned with thallium, that have been examined after death, showed the metal to be present in almost every tissue in the body,” wrote one government scientist, arguing that the element was so indiscriminately lethal that it shouldn’t even be used as a pesticide.
For several years, starting in the late 1920s, the State of California had used grain poisoned with thallium bait to eradicate ground squirrels in its southern coastal counties. As state wildlife officials discovered, the plan worked, except that it also killed animals that ate the poisoned squirrels—civets, coyotes, weasels, foxes, red-tailed hawks, golden eagles, turkey vultures—as well as any creature unfortunate enough to find leftover bait, which included mourning doves, quail, rabbits, pheasants, five species of wild geese, meadowlarks, skunks, rats, ravens, three species of sparrow, three species of woodpecker, kangaroo rats, juncos, white-footed mice, pet cats and dogs, domestic chickens, sheep, and cows.
The program was finally discontinued after a group of field workers used a sack of grain found in a grower’s barn to make dinner. It turned out to be a sack of thallium bait. Seven of the workers died, and more than a dozen others survived but suffered partial paralysis and, of course, the telltale, inescapable hair loss.
THE GROSS TRAGEDY spurred Gettler to conduct a detailed analysis of thallium toxicology. He concluded that about a third of an ounce of thallium salts would quickly kill just about anyone.
The symptoms of a concentrated dose, he wrote, were nausea and vomiting, trembling, shortness of breath, and collapse into death within about thirty hours. In fact, such symptoms were not so different from those of a virulent pneumonia, which was exactly the diagnosis of the two Gross boys to die most quickly. “In subacute cases, where the patient lives for several days to three or four weeks,” Gettler wrote, “the only characteristic sign is alopecia (hair loss) but only in those cases where death was delayed for at least 20 da
ys.”
In these gradual poisonings, the first indications were varied: nausea, diarrhea, pain in the legs, tremors, paralysis, “symptoms and signs simulating encephalitis, occasionally with psychotic manifestations such as mental depression or excitation, delirium and dementia, convulsions, coma and death due to paralysis of the central nervous system and respiratory failure.” These symptoms too could be easily mistaken for an infectious disease or sometimes a state of neurosis—and often were. In a famous murder case, a woman in Austria killed two husbands, her son, and a baby daughter with thallium between 1924 and 1934. She was caught only after she started killing lodgers in her rooming house. And that wasn’t because police suspected her; rather, the son of a formerly healthy lodger insisted that his mother’s body be exhumed, leading to an exposure of the murders.
Thallium is colorless, odorless, and tasteless. It mixes easily into liquids, without the occasional grittiness of arsenic. It can be disguised by almost any beverage—coffee, tea, soda, and cocoa. The police investigation found that Gross’s employer had recently acquired a small shipment of cocoa with the idea of adding it to the distribution list. After rejecting that idea, the company had offered the cocoa to employees at twenty cents a can. Frederick Gross had purchased four half-pound tins of cocoa shortly before his family started dying.
Surely, the Brooklyn detectives thought, that was more than he needed. It seemed he’d been planning to practically force-feed his family cocoa. Further investigation found that the import firm kept a supply of thallium sulfate on hand to keep down the building’s rodent population. The police sent one of the cocoa tins left in the Grosses’ flat to the doctor they’d been using in the investigation.
Once again he reported back that when he put the sample into the spectroscope, he saw that unmistakable, undeniable warning flash of green.
“SO FAR we have uncovered nothing that would indicate a motive except poverty,” the Brooklyn district attorney announced, but the poverty was severe: “The man had a hard time of it.”
Frederick Gross had never made much money, but the Depression had sent his finances skidding to near destitution. By 1934 his employer, the importing firm Pfaltz & Bauer, had lost so much business that it had given staffers a choice of taking a pay cut or being let go. Gross’s salary had been cut from $35 a week to $20.
The family apartment—cold water, without light or heat—cost $20 a month. That left the Grosses barely $15 a week for all other expenses. They’d taken to eating hot cereal at every meal. That was why he bought the cocoa, Gross said—it was sweet and filling. They’d had it with dinner every night—a bowl of hot farina with a little milk and sugar, and a cup of steaming cocoa. His wife often gave it to the children with lunch as well—cocoa, cereal, and a little orange juice on good days.
Even so the family was sinking into debt. Gross owned one suit—a blue serge, which he was paying off on an installment plan. On the day he was arrested, he still owed $17 out of the $30 that the suit had originally cost. The family was two months behind on rent; in April the Grosses had learned that another child was on the way. “All of it might just have been too much for him. That might have been the motive.”
The reporters picked up on the note of uncertainty in that statement. It wasn’t just Gross’s dogged insistence of innocence that caused the uncertainty. The police had found no evidence that he’d purchased or stolen the poison. No one had seen him mixing anything into the cocoa. In fact, he usually left meal preparation to his wife and mother-in-law. There was nothing to say that he had benefited from the deaths. He’d taken out no helpful life insurance policies.
Even more telling, the detectives hadn’t identified a single person who believed in his guilt. Usually, it was easy enough to find someone who’d claim that they’d always suspected the accused. But this time none of the neighbors did—none of the family or friends. His mother-in-law, still in the hospital recovering from thallium poisoning, told the police that she simply didn’t believe it. His sister-in-law said the same. Gross didn’t have a mean bone in his body, she insisted to the police, and had loved his family.
“I am confident that the mystery surrounding the deaths will be cleared up,” the Brooklyn district attorney, William Geoghan, told reporters. “Any possibility of an accident has already been excluded.” But privately he was less confident. He decided to seek the opinion of someone besides the local physician. He sent the evidence—body tissues, cocoa, the works—to the city laboratories at Bellevue.
IN CASES of thallium poisoning, autopsy results can be frustrating.
The element creates no characteristic damage, nothing like the gaudy red signal of carbon monoxide, or the bone-splintering evidence of radium poisoning. In cases of acute thallium poisoning, Bellevue pathologists found, the bodies showed perhaps an inflammation of the stomach lining, a few bloody patches in the organs, but nothing that wasn’t found in a host of other conditions as well.
Thallium doses that killed more slowly, of course, usually produced hair loss. But again, internally the poison provided nothing in the way of dramatic evidence. There might be signs of clotting in the blood vessels, fatty degeneration in the heart and kidneys, congested lungs, or an excess of blood in the brain. But two of the Gross children had been exhumed and autopsied, and in both cases “the findings were entirely negative.”
It all added up to another reason that thallium deaths were so easily and often mistaken for other causes. Only in the laboratory did thallium give itself away. In the manner of other metallic poisons, such as arsenic, thallium lodges stubbornly in the body, permeating the tissues for weeks and even months after death. Any knowledgeable forensic toxicologist can find it there.
It is, one might say, a chemist’s poison.
LIKE THE Brooklyn physician, Gettler ran a spectroscopic analysis of the tissues and the cocoa. He also saw the green flash of light with each sample. But one test wasn’t enough for him. It never was.
He went on to use a spectrograph, a piece of equipment similar to a spectroscope but with a camera to make permanent images of the lines of light. He’d found spectrographic images extremely useful in court testimony. These “photographic flashes,” as he called them, also revealed thallium in every sample of tissue.
The spectrographic lines from the cocoa, however, he found less convincing—the color seemed off to him. And the cocoa had turned a little rancid—Gettler wondered if it could have leached some metal from the can itself. He suspected the alloy used to make the container included some copper, which could account for the greenish glow of the cocoa results.
He decided to run a series of chemical tests on both the cocoa and the tissue—an old-fashioned technique, compared to the new machinery, but reliable. He repeated the tests, to his satisfaction, over a period of four days.
While Gettler was running those tests, the police began discussing an entirely different theory to explain the murders.
IN THEIR SEARCH of the Eldert Street apartment, Brooklyn police officers had found several books with Mrs. Gross’s name on the flyleaf. Two were medical books, with information on different poisons. The last was philosopher Arthur Schopenhauer’s Studies in Pessimism, which despairingly contends that at core, the universe offers no hope of a rational existence.
Geoghan, the district attorney, at first dismissed the books as unimportant, but then neighbors filed in with stories about Mrs. Gross. A woman who lived two doors down made and signed a statement about a conversation she’d had several weeks before the chain of deaths began. Mrs. Gross—after learning that she was pregnant again—had said that she intended to kill her children, her mother, and herself with rat poison.
She told the neighbor that she already had the poison and that it was slow, painless, and sure to kill. “Do you mean you’d give your children poison and see them suffer?” the horrified friend asked. She said that Mrs. Gross replied: “There’s no suffering to what I’ve got. It’s sure death.” She’d learned about the poison when she
worked as a telephone operator in a Philadelphia hospital. “It may take a day. It may take thirty days.” She just couldn’t bear to raise her children in such desperate poverty.
But, her friend told the police, Mrs. Gross didn’t want to poison her husband. Without the expense of a large family, she was sure he’d find a better life. According to the statement, she’d declared: “I have the best husband any woman could want. But rather than drudge along like this and live in poverty I’d do anything.”
The strongest objection to that theory of the crimes came from Frederick Gross, still in jail. He and Barbara had been married twenty years, since they’d met in Philadelphia. She was good woman and a good mother, he told the police. “It could never have happened that way,” he told the district attorney. “I don’t believe it.”
But the neighbors kept telling their stories, and even the prosecutor was starting to wonder.
THE CHEMICAL TESTS for thallium were an intricate, delicate business.
First, Gettler ground the tissue into slush. Then he poured in some nitric acid and let the mixture stand in a large flask for an hour. Then the flask went into a steam bath for two hours until all the tissue was completely dissolved. The solution was cooled, any solidified fat was filtered off through glass wool, and the flask was placed over an open flame. As the liquid heated, sulfuric acid was poured carefully into it.