Primary Smells, Blackcurrent, Anosmias, and Dewberry (Science-Perfume Raw Materials). Despite the lovely, and very weird, anecdote involving jasmine, black current, and the Dewberry used by The Body Shop, we decided to cut this section from the "Creation" chapter simply due to length. It is fun (and it contains an interesting experiment Turin did with "sensory burnout") but not crucial. (I present this section with the usual disclaimer: without reading the book, this will make very little sense, and you will not be able to place any of the characters or their significance).

But finally- and this is where Turin got to work applying it to his smell theory-there was the last implication thrown at him from smell's analogy to vision. The most important biological fact of vision is that it's a sense with three "primaries," primary colors- red, green, and blue- that make all other colors. That's why they're primaries. The nose-specifically the nasal epithelium, back, up, and at the top-is as chock full of receptors as the eye, and Turin was analogizing the engineering of the color sense system to the engineering of the smell sense system, and so he was saying that the smell receptors functioned like the vision receptors, and so....

Turin thought suddenly: Wait a minute. There must be primary smells. Red, green, and blue smells that make all odors in the world.

The idea of primary smells was proposed under the original Reign of Shape. It was the Greek Lucretius who first classified odors by shape. Unpleasant odors, he theorized, had hooked or barbed shapes, and pleasant odors had rounded ones. These were supposed to be the two primary odors, basic shapes that in combinations made all smells. (There are no primaries in hearing for the simple reason that while hearing is also a vibration sense- vibrations in air instead of vibrations in photons, like light-there are no individual "hearing receptors;" there is the cochlea, which absorbs all audible vibrations like a drum.) Since then, there have been ten or so different Shapist theories proposed, the Henning Prism, the Schwardmacker system, Linneaus categorization, etc., and all have tried to group odors into primaries, usually into five or seven categories (because, a psychologist might tell you, that's how many we can deal with psychologically).

John Amoore, the king of Shape, came up with seven primary odors: floral, minty, musky, camphoraceous, ethereal, pungeant, putrid. For each he posited a shape. (Musky was all cylindrical-shaped molecules. Ethereal was a sausage shape, and so on.) One odd, unexplained fact made Amoore believe in smell primaries. It had long been noticed that many people have specific anosmias, the inability to smell a molecule. Anosmias varied person to person, but they were bizarre because no one could explain why one person couldn't smell galaxolide or ambrox while another was anosmic to benzyl salicylate. So Amoore said that, well, see, these anosmias were *fundamental *insensitivity to one of the seven primaries. A nice idea. In fact, Amoore's primary shapes were ingenious, even beautiful. And they promptly turned around and bit him.

The problem was the damn exceptions. As with the rest of Shape, the more specific anosmias people identified, the more the exceptions to Amoore's general rules of shape/smell grew. Twenty, then forty, then over eighty. It was a mess. Someone turned up anosmic to some musk, they looked at the musk, and-wait, it was ellipsoidal, not cylindrical like Amoore said. Oops. Amoore was squeezing more and more bizarre shapes into the seven categories, and then he started generating more and more primary shapes until there were so many they weren't "shapes" at all, they were just descriptions of each molecule. And-and this was the important biological fact re the receptors- according to this system there'd have to be more and more classes of smell receptors, one receptor for each of these shapes. So primaries didn't work for Shape. Oh well. Most of the Shapists just tossed them aside (except Amoore, who kept muttering to himself that it should work) and went happily on.

But Turin, because he was proposing a Vibration theory of smell, faced a twist here, an implication he couldn't avoid. If smell worked like color, there should be Primary Smells. Which was to say that if Shape had maybe suggested that primaries might be a neat idea, Vibration more or less demanded them.

This was Turin being theoretical, but it seemed like solid logic. (Commercially it was also hugely interesting: Find the, say, twelve magic primary wave numbers, and every perfume in the world would contain some combination of only twelve ingredients.) Turin's interest was that he could test his Vibration theory against this implication. He could run an experiment.

Turin remembered that in late 1994 at an exhibition in London he had run into the perfumer Guy Robert and told him about his vibrational theory and this idea that there should be primary vibrations, primary smells. Robert mused for a moment- Turin watched him intently- and then remarked that once, years ago, he had walked into a hot, darkened room in southern France. Inside was a basket containing bananas and lemons, ripening in the ambient heat. When he opened the door, said Robert, the two smells hit him at once and he got… jasmine.

Jasmine? Hm! Banana + Lemon = Jasmine? Add two smells, get a third. To Turin, it sounded like Robert, with his relentlessly refined olfactory sense, had split the smell "jasmine" into its primaries.

He left for Paris, where he hung out in cafes and wandered the streets with Francoise. She lived near the Bastille, next door to a neighborhood shop that sold a terrific dirty rum from Martinique, a killer rum that gave industrial strength hangovers. He went right out and got some. That evening he was fixing a little rum. He sliced fresh mint leaves on it and brought it to his mouth. And he froze, transfixed, because he was smelling black currant. Mint + rum = an olfactory hologram of Black Currant, hovering in the air. He thought: I'm smelling black currant in its primary components.

He went back to London. He got a very cheap rum and a glass and some mint leaves and went over to Jane Brock's lab. She was working. She looked up. He put his stuff down on her various papers on tissue histology and neural connection, and she calmly watched (she'd been through this enough times) as he poured the rum into the glass, then cut up the mint and put it in. He held the glass up to her nose. She leaned over and inhaled.

She sat back, waited an instant, and said "Black currant."

He hadn't uttered a word.

Then something truly odd happened, by chance. Turin was constantly receiving pieces of information from the perfume world, which he absorbed with interest, and he now heard through the grapevine that a Quest chemist in Charles Sell's lab, a Mark Munro, had produced a 100% synthetic molecule that was supposed to smell absolutely luscious- of what, almost no one knew (it was secret). Like all molecules that hadn't yet been named, it was still called a QRM, a Quest Research Material. Turin hopped on a train down to Quest's headquarters in Ashford, Kent, to check out the smell. Munro was a very pleasant, practical guy, and before bringing out the QRM, he said So, Luca, take a look at these, and laid out for Turin sketches they were working on of a series of molecules, all variations on a structural theme. The structure was a cyclic C12, twelve Carbons on a ring, and Munro had, in fragrance chemistry fashion, attached these C12s to atom after atom to see what each would smell like. He handed Turin a vial of the basic C12. It smelled vaguely minty. Fine. Turin started smelling each variation, one after the other, with various bits and pieces joined to the Carbon ring. At each one, Munro showed Turin the structural sketch. As Munro was picking up the last vial, the new QRM Turin had come down to smell, Turin glanced at its structural formula and saw that Munro was handing him a C12 that had a chunk stuck on it called a fironone. And fironone, he happened to know, smelled like rum. So by the most complete coincidence, the QRM he'd come to smell was a minty-smelling molecule attached to one that smelled of rum.

Having never smelled the QRM, which was brand new, proprietary, secret, and closely guarded in Quest's laboratories, knowing nothing of it whatever except a sketched-out skeleton on a piece of paper, Turin said smoothly, "Oh, a black currant."

Munro blinked. He cleared his throat. "That's a pretty good guess," he said. He handed over the vial- the QRM was a spectacular, transporting, powerful, fleurescent black currant. Wonderfully clean, almost musky, none of the cat-urine note in so many black currant synthetics. He stood and inhaled it into his lungs, mesmerized, opiated. Munro, frowning, asked "How'd you do that?" Turin said "It's easy. It's two components. You want more, you know where to find me."

(This strange episode has a strange denoument. Turin went out and evangelized for this QRM, talking it up to perfumers Maurice Roucel and Calice Becker. "You've got to go smell this thing!" He went to Sell and exulted "Charles, you guys have got a terrific raw material here." But then he got a call from Sell: Apparently whatever it was that had this fantastic smell was not, in fact, the molecule drawn on the paper. Sell said it was an impurity. But, because the QRM was still secret, they wouldn't tell Turin what the impurity was. Quest has never manufactured this fantastic black currant molecule, either because they cannot manage to reproduce the impurity or because they cannot make it cheaply enough. Quest won't say. This is even more mysterious because black currant is one of the most financially lucrative smells around. Anita Roddick, a co-founder and co-owner of The Body Shop, had several years before gone to Quest to shop for smells and came across a synthetic Quest molecule with a lovely black currant smell, created by Anton Van der Weerdt, Charles Sell's boss, named neocaspirine. She loved the molecule and ordered thousands of kilos, and anyone who has been to The Body Shop knows "Dewberry," a slightly-tricky molecule they turned into a gigantic seller- slightly tricky because although beautiful, it can in certain combinations conjure an unpleasant camphor note, keeping the Body Shop's chemists on their toes. It made buckets of money both for Quest and for The Body Shop, but in Turin's view Dewberry, new to that glorious, tragically lost black currant QRM, smells like a sun-starved, second-rate little bunch of atoms.)

* * *

Turin thought he'd now try to find the wave numbers for the (apparently) primary odors of rum and mint, which was to say that he started looking for primary wave numbers. He had a terrific theory, but he had to verify it experimentally. He started, then almost immediately had to concede that rum's and mint's wave numbers were too complex to look for. But casting about, he realized there was a link to a phenomenon of the sense of sight, something called "overload" or "sensory burnout."

Smell a marigold (marigolds have hugely strong odor). Inhale the smell deeply. Now wait a second. Now try to smell it again. You can't. It's gone. You've burned out on it. You can smell anything else, but not marigold. You're "blinded" to it. Walk into a bakery, and the smell of baking bread is overwhelming. Hang out a bit, and suddenly you realize you can't smell it even if you try. And you can't smell your own house. The sense of touch doesn't desensitize. (The reason, evolutionarily, seems pretty obvious: It mustn't- we have to get away from the thorns or fire.) But the sense of hearing does; try listening to your wristwatch after leaving a nightclub.

Turin knew about marigolds and overload, of course, and he was also aware of a crucial nuance of the phenomenon: If you're hit with, say, a big smelly methyl group, or a Sulfur group, and you then try to smell another molecule that has methyl groups or Sulfurs but also other stuff as well, you will *only desensitize to the methyl or to the Sulfur. The other molecules, you'll be able to smell perfectly. In other words, burnout is extremely specific.

Turin began looking over a molecule called mercaptopinane. "Weird molecule, weird smell," he described it to Stewart. Like the black currant QRM, mercaptopinane is a molecule made of two components welded together, a mercaptan (contains Sulfur atoms, so smells of rotten egg) and pinane (a molecule that, as the name indicates, is found in pine needles and gives the "pine" smell). (When you smell pine, you're smelling Carbon and Hydrogen, incidentally.) At certain concentrations, mercaptopinane has a truly beautiful smell, of fresh pine needles and (since though most people don't realize it, grapefruit has quite a bit of sulfur, as do onion and garlic) of grapefruit.

The experiment came to him. He would use the phenomenon of desensitization to test whether the Sulfur smell was a primary smell-and thus if Sulfur's wave number of 2500 was a Primary Vibration. On May 8, 1995 he emailed Stewart: ("Subject: tremendous insight !!!") "This from home. Had a brainwave yesterday about *desensitization* to smells: If it smells of rotten eggs, you eventually tune out the rotten egg." His theory predicted that burnout is due to the receptor getting overloaded when slammed with too much of one vibration. Testing this was straightforward: He would burn himself out on Sulfur smell, then smell some mercaptopinane and find out if the Sulfur disappeared and the pine needles were left.

Here's how, he wrote Stewart.

Step One: Smell a mercaptopinane molecule. You'll be getting both Sulfur and pine.

Step Two: Grab some Big Sulfur, any Big Sulfur, which is to say grab a 2500 wave number (Sulfur's vibration) and smell it hard. Pumping a hideous Sulfur up your nose would be like shining a blinding light in your eyes: You should be desensitizing to Sulfur, your receptors burning out on (and only on) 2500 wave numbers.

Step Three: Go back and smell the mercaptopinane again. Your receptors for the 2500 wave number should be completely burned out, and only its pine needles vibrations should be getting through to you. Its Sulfur you shouldn't be getting at all.

Stewart and Turin went back and forth on which Big Sulfur to use as the blinding light, the argument arising basically because Turin was risking his life here. He was thinking about using dimethylsulfoxide, a poison, then leaned toward H2S which, he wrote Stewart with considerable understatement, was "somewhat toxic." Then Turin suddenly remembered-even better-a powerful Big Sulfur in the form of mercaptotoluene-"the most awful smell in the world!" Turin said, "except isonitriles, which are just the Godzilla of smells, you can't believe how awful they smell, they make you vomit your guts out instantly." A good blast should blind his nose to the sulfur half of mercaptopinane.

So. Time to do the test. Turin locked the door to his office and-Step One- inhaled the mercaptopinane. Yep, there were both the delicate pine needle and the sulfury grapefuit together.

He sealed that vial and opened the vial of the nasty, sulfur-filled mercaptotoluene, held it up like a shot glass, clenched his teeth, and-Step Two- with a few strong snorts knocked up several immense slugs of the molecule into his nose. (The first snort made him gag, but he kept smelling it.)

He sealed that (quickly), and apprehensively picked up the grapefruit/pine needle molecule again. Step Three. He held up the mercaptopinane and inhaled a whiff. The grapefruit- the Sulfur- had vanished. It was gone. Suddenly, all he could smell was the scent of a pine forest. He breathlessly emailed Stewart: "*Very* clear effect of mercaptotoluene on mercaptopinene, which literally smells only of pine needles after it."

Stewart: "I love that answer!"

Turin (very pleased): "yes, that was extremely clever!! check it out, it's a clever idea."

As green is the sum of the color primaries yellow and blue, a smell (Turin concluded from the phenomenon of sensory overload) is the sum of its smell primaries, which were specific vibrations.