Every morning Linus Pauling measures 18 grams of a white powder, mixes it with orange juice or water and swallows it. The substance is vitamin C, a staggering 300 times as much as the government's recommended dietary allowance.

Pauling has religiously quaffed the acidic crystals for nearly two decades, increasing the dosage from time to time to, as he believes, improve his health. He has periodically led his own studies and embraced those of others that have shown ascorbic acid, to be one of the most effective over-the-counter remedies for everything from colds to cancer.

From the sidelines, fans applaud, and vitamin producers rejoice at, the two-time Nobel laureate's cries for prevention and therapy with vitamins. But a vocal cadre of the medical community regularly and forcefully rebuts him, calling his logic myopic, naive, ludicrous and even heretical.

At a robust 85 years of age and six feet in height, Pauling stands undeterred.

"I'm in better health than when I was 65," said Pauling, who was recently in Washington to promote his new book, "How to Live Longer and Feel Better."

The book takes a step-by-step approach to reach the best possible health through a common-sense approach to diet, supplemented, of course, with a heavy dose of vitamins. Written for the mass audience, the book is Pauling's third on the medicinal qualities of vitamin therapy. Like the previous two, it strives to bring credibility to the notion that vitamins, particularly vitamin C, are not only an essential component for optimal nutrition, but also a tonic and healing agent.

Though he maintains that vitamin C should be used as an "adjunct" to other conventional forms of nutrition and medicine, Pauling, in typically blunt terms, goes to great lengths to dismiss the many physicians, nutritionists, dietitians and scientists who disagree with him.

The softly smiling and ruddy-faced man looking out of the jacket on the paperback book doesn't look much like a maverick who has been controversial throughout much of his life.

"I don't think I have a liking for controversy," Pauling said. "What I have a liking for is the truth."

Pauling, who won the Nobel Prize in chemistry in 1954 for his work on the nature of the chemical bond, says seeking truth is the driving force behind proposing ideas that may be unpopular at the time.

Naturally, others see it differently.

"Linus is a politically motivated individual," said chemist Arthur B. Robinson, who cofounded the Linus Pauling Institute of Science and Medicine with Pauling in 1973, and was later fired as its president after serving from 1975 to 1978. "He likes to chide, he likes to debate, and he enjoys the limelight."

Pauling also is not afraid of being pushed or of doing the pushing, and he seldom backs down. In 1952, when then-Sen. Joseph McCarthy [R-Wis.] arranged to have Pauling's passport revoked because Pauling espoused what he considered anti-American views, the Nobelist called McCarthy "a cancer on the body politic," and told the senator, "Nobody tells me what to think, except Mrs. Pauling."

The episode, Pauling said, awakened a sleeping scientist and sparked a need to save a silent world from destroying itself.

This quest resulted in the publication in 1958 of "No More War," a primer in the battle against nuclear war, followed by a tireless trek around the country to warn of the impending danger. Pauling collected 11,021 signatures among his fellow scientists for a petition that demanded a halt to the testing of nuclear weapons. That feat helped to spur passage of the Nuclear Test Ban Treaty, and won him the Nobel Peace Prize in 1962, the same year the treaty was ratified by the United States, Great Britain and the Soviet Union.

Pauling maintains that being right often means being alone. He often is alone on the issue of vitamin C. Pauling, who recommends that people take one to 10 grams of vitamin C a day, said: "The American Cancer Society says anyone who tells you that he has something that's good for you no matter what's wrong with you is a quack. And of course, I tell people that I know something that's good for them no matter what's wrong with them, namely vitamin C."

"Forty years ago the surgeons were giving their patients what they considered to be high intakes of vitamin C to speed up recovery," Pauling said. "I have a feeling they've the medical community sort of forgotten about that." Pauling first heard of the positive health effects of vitamin C in 1966, shortly after being awarded the Carl Neuberg Medal in New York. In his acceptance speech he remarked that he hoped to live another 15 to 20 years to witness the miracles of science and medicine that were sure to follow.

Biochemist Irwin Stone, who then worked for a New York pharmaceutical laboratory, was in the audience, and had just the thing. In a letter to Pauling one month later, Stone praised the medicinal qualities of ascorbic acid, or vitamin C, and included four research papers he wrote confirming that the daily intake of vitamin C improved one's health. Stone said he took three grams a day. Pauling became interested in Stone's observations and he and his wife, Ava, began a three-gram-a-day regimen. After three years, "we discovered that we no longer caught colds," and they increased the daily dosage to 10 grams.

Pauling embraced the study of vitamin C with a religious fervor, and in 1971 published "Vitamin C and the Common Cold," in which he and Scottish physician Dr. Ewan Cameron claimed that if ingested daily in small amounts, vitamin C could decrease "the incidence and severity of the common cold in subjects under normal exposure to virus infections."

Physicians, however, were hostile to the proselytizing Pauling.

Dr. Charles C. Edwards, then commissioner of the Food and Drug Administration, retorted: "There is no scientific evidence and never have been any meaningful studies indicating that vitamin C is capable of preventing or curing colds."

The criticisms didn't matter. Pauling's message got through loud and clear if for no other reason than the fact that he is the only person to have received two unshared Nobel prizes.

"Vitamin C and the Common Cold" has sold more than 300,000 copies, and vitamin C sales skyrocketed over the past decade, increasing an average of 17 percent a year from 1976 to 1983. Vitamin C sales alone account for $350 million of a $1.3 billion-a-year vitamin market.

Pharmaceutical companies generally say the increasing attraction of vitamin C is fed heavily by a health-conscious public, though some company spokesmen acknowledge that the increase in part can be traced to his claims, which they openly embrace. Still, Pauling's views are called suspect by many scientsts who say that he recommends vitamin C at a pace that would make the average vitamin salesman marvel.

In 1979, Pauling raised the stakes when he and Cameron recommended vitamin C for treating cancer. In their book, "Cancer and Vitamin C," Pauling seemed to put his credentials on the line to make vitamin C a cause celebre. He claimed that the incidence and mortality from cancer could be decreased 75 percent by the proper use of vitamin C alone.

Rebuttals were issued from every corner of the scientific and medical communities, pointing out that there is no evidence to support such claims.

"In terms of direct anti-cancer therapy, vitamin C has no role," said Frank J. Rauscher Jr., senior vice president for research at the American Cancer Society. "Like many nutrients, it probably doesn't do any harm, and may do some good. I think the studies that have been conducted unfortunately very well prove that any of his [Pauling's] claims are without merit."

"Dr. Pauling is a creative investigator," said Dr. Peter Greenwald, chairman of the division of cancer prevention and control at the National Cancer Institute. "To his credit he's given attention to diet and prevention."

But Greenwald delivered a common demur when he added: "He's basically a chemist," and lacks the medical credentials to prescribe vitamin C.

Nonsense, Pauling retorts. "Although I don't know the art of practicing medicine," he said, "I do possess scientific training, more than some medical researchers."

Thomas H. Jukes, a professor of biophysics at the University of California at Berkeley, who has followed Pauling's career, called his claims "exploitive . . . a terrible deception to the public," and warned that Pauling's push "may divert people from getting therapy that might be useful to them."

But the debates may have as much to do with the egos of scientists as with science itself.

"Take Dr. X. He's been working on cancer for years and there are a lot of things that he can't figure out. Then this upstart comes along and says: 'Here, take vitamin C. It'll work,' " said Harden McConnel, a Stanford University chemist, and former student of Pauling's at the California Institute of Technology. The debate is intense and sensitive not because it revolves around right and wrong, which it may, but also because it involves the encroachment on someone else's niche.

It was Pauling who insulted Britian's Sir William Henry Bragg and his son William Lawrence by studying their work in X-ray crystallography in the late 1920s and improving on it. Pauling successfully traced the forces of stability in crystals and had them codified into six principles, a set of rules seized upon by crystallographers around the world.

And it was Pauling who in 1949 plunged into medical research by revealing the distortion in hemoglobin that gives sickle cell anemia its name.

Pauling has made a career of taking the unpopular stance, only later to be redeemed.

Edward Crellin, one of four of Pauling's children, who at 49 years old heads the biology department at San Francisco State University, said his father's tenacity and stamina are inbred.

"He comes home from a trip and he reads what's in the journals that have come in the mail, and finds something he doesn't agree with and writes a letter," Edward said. "It's something that piques his curiosity. That's his idea of recreation."

"My father was very much involved in his world of molecules and he left 'mundane' things to my mother to take care of," he said. "You don't accomplish what he has without working 18 hours a day. I can never remember throwing a baseball with him. Leisure as most of us define it is nonexistent to him."

Whether Pauling's appeal is strictly limited to vitamin producers and prevention gurus or extends to the general public is difficult to measure. But the maverick scientist may have lost substantial respect when he fired Robinson in 1978 over what Robinson claims were negative results of a mice study that was embarrassing to Pauling.

The study of 900 mice over several years found that the incidence of skin cancer was decreased most significantly among groups that received a diet of pure fruit and vegetables and huge quantities of vitamin C (the equivalent of 50 grams a day for humans.) But Robinson found that mice who received a regular diet supplemented with the human equivalent of three to 10 grams a day of vitamin C fared the worst, developing lesions at a much faster pace than any of the other control groups.

The study suggests that the daily doses of vitamin C recommend by Pauling (3 to 10 grams a day) are actually harmful.

Pauling called the study "amateurish," and though he denies a correlation between the experiment and Robinson's dismissal, he refused to allow Robinson to publish the findings, in what became one of the most heated exchanges between scientists in recent times.

Robinson sued over his dismissal, which was from a tenured position, and claimed that Pauling had dragged his scientific credentials through the mud. A five-year legal battle ensued, at which point Pauling, or the Institute, paid Robinson a settlement of $575,000. The court-approved agreement states that $425,000 of the settlement was for slander and libel and the balance was for attorneys' fees and other expenses.

Pauling, who says he hasn't had "any down times" during his life, with the possible exception of the McCarthy episode, would prefer to forget about Arthur Robinson and continue to research cancer and tell the world about his many discoveries.

But that won't ever be easy.

"A scientist has an obligation to prove himself wrong, to think of constructs that defy the picture," Robinson said. "Only when there are none left can he claim that there's something to it. He Pauling finds things that prove him right. That is a fault that has been with him for a long time."

Jukes agreed, saying: "He's always got an escape hatch. He may be a true believer, but he's got blinders on."