IN HIS SECOND hearing before the Senate Foreign Relations Committee, Kenneth Adelman abandoned the smile-and-nod strategy of his unfortunate first appearance and allowed even his more partisan interrogators to see him for the qualified, articulate person he is. So it is said he will not have serious trouble in receiving the committee's approval today for his nomination as arms control director. We hope this is so.

Meanwhile, it seems that the hitch in Mr. Adelman's confirmation has had one positive byproduct. Committee Chairman Charles H. Percy took the occasion of the administration's temporary embarrassment to demand action on two lesser Nixon- Ford nuclear treaties, the one limiting underground weapons tests and the other limiting peaceful nuclear explosions to 150 kilotons--10 times Hiroshima. The upshot is that a seven-year bureaucratic logjam may now be breaking.

The Ford administration did not have the time to carry off ratification of these twin treaties. The Carter administration went for broke--a ban on all underground tests--and got nothing. Until now, the Reagan administration has pleaded dissatisfaction with the agreements' verification provisions, even while some officials, intent on resuming tests of high-yield weapons, have conducted what former arms control director Eugene Rostow termed a "profound stonewall."

Of this last consideration, Gen. David Jones, former chairman of the Joint Chiefs of Staff, has declared that the country's arms requirements can be fully served under the two treaties' terms. Both countries have in fact pledged to keep their weapons tests (and Moscow its peaceful explosions--we conduct none) under the agreed ceiling. The cutting issue is verification. Not only has experience raised specific questions about the provisions negotiated in 1974-76, according to the Pentagon, but also the Soviets' contemptuous violation of their treaty promises on chemical and biological warfare has sharpened the general question of the value of their word.

President Reagan is now considering textual changes to broaden the two treaties' ground-breaking on-site inspection provisions. Because the treaties were not ratified, these provisions have never been invoked. Mr. Reagan's purpose--to reduce uncertainty --is unexceptionable. To demand too perfect a degree of certainty in verification, however, is the familiar formula for killing an otherwise meritorious arms control proposal. Chairman Percy has usefully warned that new proposals should not beg Soviet rejection or invite endless negotiation on what are, after all, details of solemn agreements already made.