A District of Columbia narcotics-control bill that would double penalties for selling hard drugs to teen-agers won preliminary approval yesterday from the D.C. City Council.

The measure, which on final passage would add a new weapon to the arsenal of weapons available for the city's crackdown on the illicit drug trade, is similar to congressionally enacted legislation that is already in effect here because -- in some applications of criminal law -- the District is considered federal territory.

One main effect of the new legislation, council Judiciary Committee chairman David A. Clarke (D-Ward 1) said, will be to transfer the prosecution of an estimated 250 to 350 drug cases a year from U.S. District Court to the city-run Superior Court.

The D.C. Uniform Narcotic Drug Act enacted by Congress in 1938, currently the city's basic antidrug law, provides penalties of only up to one year in jail for drug sellers regardless of the type of narcotic involved.

The new legislation would provide for jail sentences ranging from one year for the distribution or sale of marijuana up to 15 years for a similar violation involving such hard drugs as heroin, LSD or hashish. An adult who sells hard drugs to someone under the age of 18 could have the penalty doubled -- a term up to 30 years. Cash fines also could be assessed.

In voting the new legislation, the council voted 10 to 3 to reject a proposal by John Ray (D-At Large) to impose mandatory jail sentences or fines for serious violators. Ray's proposal was opposed by the local branch of the American Civil Liberties Union and a coalition of political, racial and public-interest groups. Only Nadine P. Winter (D-Ward 6) and Betty Ann Kane (D-At Large) joined in voting for Ray's proposal.

The new bill is similar to the basic nationwide federal narcotics law and the laws of 42 states, including Maryland and Virginia, that have adopted a uniform nationwide measure to control illegal narcotics.

The new measure is subject to final enactment, probably in two weeks. If signed by the mayor, it is subject to review by Congress.

On another matter, the council voted approval of a bill by John A. Wilson (D-Ward 2) to permit, under some circumstances, the demolition of apartment buildings located in commercial zones if they are to be replaced by commercial buildings (but not by hotels). The owners first must offer the apartment buildings for sale to their tenants. Before demolition, they must obtain a building permit for the new structure.