Two months ago Dr. Linus Pauling happened to think about cataracts.

The eye disease reminded him, he said, of the way boiling makes the transparent white of an egg opaque.

Possibly, he theorized, cataracts are created by some similar chemical change in the submicroscopic molecules of protein that make up the human lens, or the window of the eye.

What is the change? Pauling asked. What causes it? What chemicals--vitamins perhaps; vitamins are an important Pauling cause--might retard it?

For Pauling--discoverer, political activist, vigorous man at 82--the search for the cause and cure of cataracts is about to become the latest of hundreds of projects that have won him two Nobel prizes and, this year, the Priestley Medal, the highest honor of the American Chemical Society.

Joseph Priestley, an 18th-century English thinker, discovered oxygen. The Priestley award, announced yesterday at the society's annual meeting here this week, is in recognition of Pauling's stature as perhaps the world's leading chemist.

It is also a sign of his returning respectability. He has been intensely controversial for decades, most recently for his zealous advocacy of vitamin C for colds and cancer. As many scientists say today, "I think some of his current ideas are probably right. I just don't know which ones."

Pauling is just back from public meetings in Germany, helping scientists there state their opposition to nuclear proliferation and the placement in Europe of U.S.--and, he said, Soviet--missiles. Shortly he will be off to Germany again on the same mission.

"I have always felt grateful that the nuclear deterrant was developed," he said, "because it requires that we abolish war from the world. I think it has already served to abolish war between the great powers . . . . No, I am not advocating nuclear disarmament . . . .

Does he think, despite all, that there is any chance of getting nuclear weapons under control?

"Yes, I do think so," he said, "because otherwise I wouldn't be wasting my time" in anti-nuclear talk. "I'd be enjoying myself."

How?

"Making quantum mechanical calculations."

Pauling began thinking about the structure of molecules in 1919, when little beyond theory was known about these basic chemical structures, these atom-by-atom constructions that make up all matter.

In the years ahead, he was among the first to seize on two new techniques for determining a molecule's structure: electron crystallography, using X-rays to take a picture of a molecule's atoms, and electron diffraction, in effect taking similar pictures by bouncing electrons off the otherwise invisible structures.

In studies in Europe in the mid-1920s, when Europe still ruled the scientific world, he also studied the new theories of quantum mechanics: the mathematics of matter, equations scientists use to predict matter's behavior.

Pauling's resulting descriptions of the chemical bond, the way molecules are held together, won him the 1954 Nobel prize in chemistry.

Chemical and Engineering News, the chemical society magazine, recently toted up the results of Pauling's ongoing research.

He showed that diseases could be caused by changes in the molecular structure of proteins, and that sickle cell anemia is just such a "molecular disease," the result of a single misplaced amino acid on the hemoglobin or red blood cell molecule.

He and Robert Corey established that human genes are put together in a screw-like helix or long chain of molecules. He barely missed describing the complete double-helix form of the gene, which undoubtedly would have won him a second Nobel prize in science.

He won the Nobel peace prize of 1962 for his anti-war crusading, also the Soviet Union's Lenin Peace Prize and its Lomonosov Medal, its highest scientific honor.

This does not mean he considers himself in tune with the Soviets. He recently said, "I criticize the United States for increasing military expenditures because I am an American."

Pauling has won most public notice recently for using his molecular theories to create what he calls "orthomolecular medicine" based on molecular manipulation, a field that he admits is occupied by "some doctors I trust" and "some people on the fringe."

As part of orthomolecular medicine he advocates daily doses of vitamin C to prevent colds and even larger doses to abort them. He said he believes experiments will show that large amounts of vitamin C, while "not a cure" in itself for cancer, will help cure cancer if properly used in conjunction with conventional therapy.

He does not just praise vitamins. He takes them: 12 to 40 grams a day of vitamin C, meaning whole spoonfuls of lemony-tasting powder every morning and "a pill every now and then during the day, when I think of it;" a super-B tablet; vitamin A; vitamin E; a standard vitamin-and-mineral pill "for the minerals," plus "some extra" zinc and selenium.

He said he regrets that the federal government hardly has begun to finance the research to show that such substances are important and "how much of them" people really need.

In 1980, after applying every year since 1973, he got his first National Cancer Institute money, 00,000 a year for two years to study the effects of vitamin C on cancer in mice. Not much on the federal books, "but 5 percent of our $2 million budget" at the Linus Pauling Institute of Science and Medicine in Menlo Park, Calif.

So as he thinks about that new research on cataracts now, he concluded, "I'm in the process of thinking about how to raise the money to do it."