At 11:32 p.m., Thursday in a crowded conference room built by a now-bankrupt financier, 6 1/2 years of negotiation and preparation of the new Strategic Arms Limitation Treaty (SALT II) came to an end with a handshake and a round of applause.

The handshake was by Ralph Earle, a Philadelphia lawyer who has been the chief U.S. negotiator in Geneva for past six months, and veteran Soviet diplomat Viktor Karpov, who has been the chief negotiator for his country in Geneva for about the same length of time. The applause was from 70 working members of the two delegations in Geneva, who had been summoned to a final general meeting.

The setting was the eighth-floor conference room of the U.S. SALT mission in Geneva. The building was built by Bernard Confeld, a failed financier, for his then-booming Investor Overseas Services Inc. The U.S. acquired the lease on the top five floors of the building after Cornfeld's financial house of cards collapsed, leaving investors in the lurch.

Earle and Karpov had actually picked the last sticky nit in the SALT negotiations in the wee hours of Thursday morning at the Soviet mission, a high-ceilinged villa that wa formerly headquarters of the Lithuanian mission to the League of Nations.

As often is the case in the long years of SALT bargaining, the final business was a question of insignificance in the grand scheme of strategic nuclear power - but a matter which would have been of grave and even mind-boggling importance in an earlier age.

The Soviet Union years ago built at Tyuratam near the Caspian Sea 18 missile launch sites for fractional orbital bombardment systems. These are missiles fired beyond the atmosphere into a partial orbit in space before diving to earth with their nuclear warheads.

Development and testing of such fractional orbital systems are banned under the terms of SALT II, so these 18 sites are of no more use. The Soviets propose to dismantle 12 ot them, but wish to retain the right to convert the remaining six to test sites for standard intercontinental missiles.

The question was: What would the Soviet be allowed to do at these missile sites without having them count against the SALT II% limit of 2,250 strategic system? The final wording of the final agreement of this long running negotition was that the Soviets at the six sites would be limited to "normal maintenance required for launchers in which missiles are not deployed."

If that seems obscure, remote and the stuff of some far off world, the same could be said of much of the rest of the myriad details of SALT II, one of the most highly detailed and technical international documents ever drawn. The treaty to be signed here by President Carter and Soviet President Leonid Brezhnev on Monday is more than 70 pages long, and it is almost inpenetrable in some of its language and meaning to all but the best-informed experts.

Carter and Brezhnev are also expected to discuss a successor treaty, SALT III. That could be important not only for the momentum of successor negotiations but also in the Senate struggle over ratification of the SALT II treaty. Signs of Soviet willingness to be accommodating on future deals, particularly in the area of vertification, could smooth the bumpy road in the U.S. Senate.

The basic goals for SALT III, as agreed by the two sides are:

A start on the new treaty immediately after the ratification of SALT II.

Significant reductions in weaponry.

Further qualitative restrictions on weapons.

New limits on strategic defenses.

Cooperative measures to improve verification.

In the meantime the SALT II treaty, the legalistic but epochal document that is the formal reason of this Vienna summit, has arrived here in the briefcase of the U.S. negotiator in Geneva.

Some officials, not including Earle, thought that the security risk to 61/2 years' precious work was important enough that a special U.S. Air Force plane should be sent to Geneva to fetch them.

After a debate Earle brought the complicated document here in his briefcase - by a commercial flight.