WE PUBLISH on the opposite page today an appeal by four senators for the United States to end its self-imposed 16-year moratorium on the production of chemical weapons. To make it more certain that the Soviets will not use or flaunt their fully modern chemical weapons, the four argue, this country should go ahead and produce new ones to replace the old ones in the American stockpile. Further advantages, in safety of handling and in possibly facilitating negotiated Soviet-American cuts, are also claimed.

It is an earnest argument, but an unconvincing one. Why is it, after all, that chemical arms remain the one major weapons system requested by the Reagan administration that Congress has consistently refused to approve? The reason lies, we believe, not just in people's squeamishness about one deadly branch of military technology; there are many deadly branches. It lies in the logical expectation that deterrence of chemical warfare does not have to be accomplished by the threat of chemical retaliation: it can be accomplished by threatening retaliation with conventional weapons. That is the situation now.

Unmentioned by the four senators, moreover, is the one particular scenario that most analysts think of first when chemical weapons come up: the use of them to support an invasion of Western Europe by conventional Soviet forces. Some military commanders, observing the Warsaw Pact's preparations for chemical warfare, suggest that NATO should be better prepared to respond in kind. Wisely, however, Europe's politicians have respected their publics' long-evident dread of seeming to condone, by preparing for, this form of combat on their home territory. The alliance is not currently so free of other strains that it can lightly tempt the major new tensions that would follow an American decision to build more chemical arms.

The better course is to stay with the United States' 16-year abstinence from making new chemical weapons and to continue to keep the onus on Moscow as the one great power that actively threatens to use, in a populous zone in the heart of Europe, a weapon with a special connotation of horror.