(FORTUNE Magazine) – PALL CORP. There's money in separating the wheat from the chaff. David Pall, 76, a chemist who helped design a filter for the Manhattan Project atomic program in 1941 -- it winnowed uranium 235 from the less stable uranium 238 -- went on to build the successful company that bears his name. It makes specialty filters for various industries, including aerospace, beer, chemicals, cosmetics, paint, and pharmaceuticals. One of the company's newer products: a blood-transfusion filter devised by a research team led by founder Pall and introduced in 1988. It removes virtually all the leukocytes, or white blood cells, that can cause a patient to reject transfusions. Rejection is a particular problem for patients who need multiple transfusions while undergoing chemotherapy, organ transplants, or treatment for AIDS. Morgan Stanley security analyst Mark Gulley believes that the blood filter is Pall's ''most exciting product.'' The company sold $50 million worth of them in 1989, about 10% of the year's $497 million in sales. It expects blood-filter revenues to increase 40% this fiscal year, which ends in July. Pall Corp. is doing especially well overseas. Foreign sales accounted for 60% of 1989 revenues. Among the foreign customers: European breweries and wineries that use Pall filters to remove yeast and bacteria. Pall makes about 80% of the products sold overseas in its own plants abroad, mainly in Europe. Explains CEO Maurice Hardy, who built the international operation: ''The 1990s are going to be a decade of protectionism. American companies need to have manufacturing capabilities overseas or they will suffer.'' Over the past 18 years, in the face of heavyweight competition from the likes of Baxter International, Millipore, and Parker Hannifin, Pall's sales have increased at a compound annual rate of 18%, profits at 35%. Pall earned $57.7 million in 1989, and Morgan Stanley's Gulley expects 1990 earnings to be $69 million, up 20%, on revenues of $575 million. Even more impressively, Pall has pulled this off mostly by internal growth; the company has made only two small acquisitions in its 44-year history. Investors have taken note. Pall's stock traded on the American Stock Exchange recently for $35, 19 times 1990's . anticipated earnings.

LINDSAY MANUFACTURING They know a lot about what drought can do to crops in Lindsay, Nebraska, headquarters for this maker of irrigation systems. Traditional surface systems, still in use on 60% of the irrigated land in the U.S., release water at the higher end of a slightly sloped field. Lindsay's center pivot machines resemble a giant single-spoked wheel made of pipes propped 11 feet above ground on a set of rolling towers. The spokes, some of them up to 1,300 feet long, rotate around towers in the center of each field. A microprocessor controls the flow of water. Such systems, which are made by a number of manufacturers, can irrigate up to three times the area per gallon that the more common surface irrigators do. Another advantage: more efficient use of the fertilizers, pesticides, and herbicides that may be mixed with the water, which helps reduce potentially harmful runoff. Lindsay's 1989 revenues were up 22% to $92.6 million, and profits nearly doubled to $7.3 million. The stock traded recently for $31, eight times 1990's estimated earnings.

A&W BRANDS America's taste for fizzy sweets has been good to this White Plains, New York, company. On average, each of us guzzles about 45 gallons of soft drinks every year, and A&W has carved itself a 1 1/8-gallon niche. Rather than going head to head with Coca-Cola and PepsiCo, which dominate the market for colas and lemon-lime sodas, A&W brands have seized the biggest niches in root beer, grapefruit and cream sodas, and ready-made lemonade. A&W often uses the same bottling companies as Coke and Pepsi. Says Emanuel Goldman, a Paine Webber analyst: ''One of the most important things in the soft drink industry is to get the bottlers on your side, because they get the shelf space. A&W gets on very well with the bottlers.'' A&W was part of United Brands until 1983. It went through two buyouts before going public in 1987. The stock trades for about $30 a share. Last year profits rose 34%, to $10 million, on sales of $110.9 million, despite an extraordinary $500,000 charge. Analysts expect earnings to grow at about 20% annually.

ENTERTAINMENT PUBLISHING Nobody loves a two-for-one deal more than Hughes Potiker, chairman of Entertainment Publishing. His Troy, Michigan, company prints and sells coupon books that offer discounts on sports events, plays, concerts, and restaurant meals, typically as twofers or at a 50% discount. Nonprofit groups are the usual customers; they then sell the books in fund-raising efforts. The company also designs coupon books for customers like American Express and RJR Nabisco that use them in promotions and as sales incentives. Last year Entertainment Publishing made $4.2 million on sales of $74 million. In the first six months of fiscal 1990, which ends in June, profits jumped 74% on a 12.5% rise in revenues. New offerings being test-marketed include Baby Bonanza, a book of coupons for new parents. The company is also testing Bed and Breakfast Plus, an international directory of such hostelries. Entertainment Publishing's stock sold recently for $16 a share, about 12 times projected earnings for the year.