Saving formula for the second canal treaty facing U.S. Senate action today, is already preparing to ride out the storm of protest that is expected to follow here.

The decision to accept a balancing reservation after what is described here as the "insult" of the DeConcini reservation on the first canal treaty is a severe blow to the Panamanian leader. He faces fierce protest from a broad political front and he received a first taste of it yesterday.

As schools and the university reopened after a prolonged Easter recess, the 5,000 students of the National Institute - the radical and most prestigious high school - refused to allow Torrijos to make an announced visit to the school.

The students sent word that he could not enter the school unless he rejected all American treaty amendments and reservations, and pledged the return of Panama's political exiles. Torrijos did not go.

At mid-morning, about 100 leftist students from the university law faculty bombarded the U.S. Embassy with soda bottles filled with red, white and blue paint, the colors of the Panamanian flag. The students had marched from the university campus to the embassy shouting anti-American and anti-treaty slogans. They left the embassy splattered with paint.

Panamanian national guardsmen dispersed the crowd with tear gas but no arrests or injuries were reported.

Tensions have been high in Panama since passage last month of the reservation introduced by Sen. Dennis DeConcini (D-Ariz.) declaring the American right to use military force against Panamanians to keep the canal open.

Yesterday officials were hastily preparing government strategy and conversations with a variety of them suggest the following scenario:

If the Senate adopts the second treaty today, the government will publicly accept both treaties provided the face-saving formula is included. Its actual text wks not revealed here.

A high official is then to make a statement to the nation, explaining the government position and emphasizing the conquests the treaties represent.

The government will oppose pressures for a new plebiscite. Panamanians voted ratification four months ago of the original treaties language. The government has begun negotiating with key political groups, including the moderate LIERAL Party, to withdraw its opposition to the pacts in exchange for some participation in the government, possibly after presidential elections in August.

Torrijos expects to ride out the awaited storm of protest and tolerate the student demonstrations as long as they do not cause serious violence.

Key analysts here fear it may not be simply a matter of riding out a short storm, however. The American control over the canal has been the main foreign policy issue for more than 70 years and Panamanians have declared vehemently that the military intervention clause, as spelled out last month by DeConcini, throws Panama back more than 40 years.

In 1936, the United States eliminated the article written in the original 1903 treaty which gave the United States the right to enforce "the maintenance of public order in the cities of Panama and Colon and the territories and harbors adjacent thereto, in case the Republic of Panama should not be, in the judgment of the United States, able to maintain such order"

DeConcini's reservation, which insisted on the U.S. right to use force if labor unrest or political trouble in Panama closed the canal, is seen here as amounting to exactly the same thing.

No amount of American or Panamanian government fudging, treaty opponents say angrily, can cover up the fact that the hated DeConcini clause survives. Legal experts point out that the canal treaty to be voted today, wihtts face-saving reservation, would expire in the year 2000, while the earlier neutrality treaty, including the DeConcini reservation, is permanent.

Gen. Torrijos, asked in an interview with ABC News what language in a new reservation would be acceptable to him, replied:

"Something . . . establishing that nothing that was said before would mean that the United States would interfere in. . .the internal political life of the sovereign integrity of this country."

Asked how he thought the DeConcini reservation came about, Torrijos replied, "Since this language has not been utilized since the last century, we were not prepated mentally that it should come up in this discussion of the treaties." He referred to the reservation as offensive.