In the two years since bloody student rioting in Soweto focused world attention on the depth of the grievances among South Africa's blacks, the country's white minority leadership has begun discarding many of the most glaring practices of social, economic and educational discrimination.

But the government also has made it clear that it will not surrender political dominance - and this has left blacks angry and dissatified.

The ruling National Party, controlled by the country's 2.6 million Afrikaners of Dutch descent, has not abandoned its basic philosophy that blacks and whites must have their own separate local, regional and national governments and that whites must maintain overall control for many years to come.

Yet it now appears to believe that opposition to this policy can best be dissipated by easing some racial discrimination, accelerating the economic and social advancement of blacks and granting a measure of local autonomy to urban black communities.

While it makes these concessions, however, the government also is using an iron fist against political dissidents who are turning to more violent means of protest. This is shown by recent security police announcements that scores of alleged "terrorists" have been captured and by the mounting numbers of arms caches seized.

The changes are being implemented against a growing black-white polarization that accounts, in part, for the divergent responses to them.

To most whites, improvement in the status of blacks is coming fast and furious. "You should have seen what it was like five years ago," is the constant refrain to visitors. Government officials urge foreigners to understand that while the changes may not seem important to them, "They are big changes to us."

Although most of the reforms have been made since the National Party received its largest mandate in history in an election six months ago, the pace of change is carefully regulated to avoid inflaming latent right-wing sentiment. In some rural areas this sentiment prompts whites to refer to blacks as "Vorster-children," insinuating that Prime Minister John Vorster has taken blacks under his wing.

The general black response to the changes is indifference, an attitude of "too little, too late." Black political leaders say their basic grievance - the refusal of whites to share national political power - continues to be ignored.

Vorster has made it clear that the country's 18 million blacks can exercise their right to national self-rule only in the nine tribal homelands set aside for them. The 4.5 million whites, 17 percent of the population, will continue to rule over the rest of the country, which includes the major urban areas and 87 percent of the land.

Asked about the changes, a black cafe owner said, "I admit there have been a lot, but they are meaningless. Look, women are fond of changing around their furniture, but it's still the same old house."

Bishop Desmond Tutu, general secretary of the South African Council of Churches, recently listed three things the government could do that he said would represent significant change to blacks, call a national convention of all races to work out a new political system; scrap the detested "pass laws" that restrict black migration into the cities and grant full property ownership rights to urban blacks.

The government's approach to these issues clearly defines the limits of the changes it will accept.

It has no intention of calling a national convention because, it says, its separate development policy is "non-negotiable."

In the case of the pass laws, the government, seven months after announcing it was preparing to relax the rigid requirement, proposed slight modifications that would leave it in effect with merely the surface appearance of change. It said that papers issued by homeland authorities could be used as pass books only if the book itself is not more than three miles away.

On the third issue, however, the government has made a major concession. It will allow blacks to acquire 99-year leases on their homes in urban areas but not on the land underneath them. The change gives black leaseholders more security and allows them to rent or sell the buildings, bequeath them to heirs and raise loans for improvements - all of which were not possible before.

This change. The minister of black affairs, Connie Mulder, said a would give a degree of permanence to blacks, who up to now have been regarded as temporary residents in urban areas.

Title to land could not be allowed. Mulder said because it would give blacks the right to vote in white areas, which is forbidden under apartheid, as the separate development program is called.

The move, however, falls short of the blacks desire for 'unfettered freehold tenure."

The Johannesburg Post, a black oriented newspaper, commented: "The government has let another opportunity to prove its sincerity slip by . . . The black population certainly expected much more than is contained in their present "new deal" . . . Home ownership is a basic right to which every citizen is entitled."

Mulder has also inaugurated a system of local government in urban black communities, promising that it will lead eventually to complete autonomy in local affairs. It has had only limited success so far and in Soweto, a black suburb of Johannesburg that is a bellwether for black politics in the country, the council has been a conspicuous failure.

Because of a boycott to protest the detention of black leaders from Soweto, the council members were elected with only 6 percent of the eligible voters participation. The council is so touchy about its position that it barred black Johannesburg Post reporters from its first meeting.

One of the most visible signs of change is the gradual opening up of theaters, hotels, restaurants, sports and nightclubs to all races. The government has set a few token examples by opening up luxury train compartments, station facilities and its new multimillion-dollar opera house. Local authorities now have the power to permit establishments to serve blacks - but that is the catch since local bodies very often choose not to desegregate. Critics say this system simply moves discrimination enforcement from the national government to the private sector and local bodies.

Easing of racial barriers has so far occurred only in expensive establishments, out of the financial reach of most blacks. A recent survey by the Financial Mail Magazine found that only 49 of the country's 1,448 hotels admit all races, and there are limiting restricitons even at these.

Many black youths spurn the newly integrated establishments as part of trend to refuse all contract with whites. "I wouldn't tell any teenagers I know that I've been here tonight," said a middle-aged black businessman enjoying a drink in a multiracial nightclub.

Significantly for those who say the government shirks its duty, one of the most significant steps forward - moves to end discriminatory labor practices - was the work of private industry leaders.

In November the government nullified most legislation reserving certain jobs for whites or "coloured" (mixed race) persons. While in theory this represented a significant shift, it amounted to little more than recognition of a de facto situation because most of the jobs affected were already filled by blacks through exemptions obtained by their employers.

Yet, the government's action laid the groundwork for what has been hailed as a "major breakthrough." Two weeks ago when employers in the steel and machine tool industries, including a government-owned steel company, forced the powerful white trade unions to drop the racial bar in their new wage contracts, the government welcomed the move.

The action means that hundreds of job classifications formerly barred to blacks, are now theoretically open. Only the top artisan level is still restricted by union-controlled apprentice programs. Making this change meaningful, however, now depends on the industries' efforts to give blacks the necessary skills.

Several small changes have done little to alter the situation. The word "bantu" has been replaced in government documents by "black," churches no longer need to get a permit for multiracial worship but most were already doing it without one. Private white schools can admit nonwhite students and ambulances while segregated, may now carry patients of any colour in an emergency.

Some changes, like those in sports have left the public confused. Although Sports Minister Piet Koornhof says there is no barrier to mixed sport, two weeks ago, a white rugby player participating in a mixed game was convicted of being in a black area without a permit and last week, six black athletes were barred from a race in a white area.

In public education, while the government has begun giving free textbooks in the higher grades, has increased black teachers' wages and started programs to improve their training, it still spends about six times as much on white education as it does on black. It has promised to make the black system more equivalent to that of whites.

Despite all these changes, the government shows no sign of sharing power with the black majority. Instead, it hopes to secure its position by bringing the country's 2.6 million coloreds (persons of mixed race) and 750,000 Indians into the system under its new constitutional proposals. Both nonwhite groups, however, are divided on whether this offers them meaningful powers.

The plans hold no such offer for the blacks. Mulder's recent remarks that "there will be no black South African citizens" under the separate development program because they will all be citizens of a cast-off homeland has had great impact on blacks.

"The citizenship thing is the explosive issue. The kind of cuckoo-cuckoo land they are trying to set up is causing a lot of frustration," Tutu said.

"To us blacks, South Africa is our fatherland, the whole of South Africa, and the subterfuge will change that," said Soweto leader Nthato Motlana.