The hospital says it already provides millions of dollars in free care, but the charity said it needs to do more to fulfill the pledge it made to Lippitt 96 years ago.
"It just seems illogical to me that a quote-unquote 'permanent free bed,' which by its very name suggests that it is to last forever, can somehow not last forever," said Mark Swirbalus, a lawyer for the organization.
If it had been modestly invested, Swirbalus said, Lippitt's donation could be worth about $1.5 million today.
On Tuesday, a judge will hear arguments on the hospital's motion to dismiss the lawsuit.
Rhode Island Hospital was among many facilities, especially in the Northeast, that had "free-bed funds" through which donors could set aside a hospital bed for the poor.
In Rhode Island Hospital's case and others, officials say interest from those funds continues to help cover health care costs for people who can't afford them, though not through a specific hospital bed.
Hospital spokeswoman Gail Carvelli said the money donated for free beds was put into a restricted account that pays for charity care, but she could not say how much was in that account or how much of its funds are spent annually.
Swirbalus said Children's Friend does not expect the hospital to set aside a bed that would be available only to the charity's clients. Rather, the charity wants to ensure its clients receive free care in whatever bed they're treated.
Carvelli says Rhode Island Hospital honored its commitment until the charity Lippitt chose stopped nominating patients, though she was not clear when that occurred.
The 719-bed hospital also argues that Children's Friend and Service does not have standing to sue because it did not even exist when Lippitt died and is separate from the charity she named in her will, Children's Friend Society of Providence. Children's Friend and Service says it's a successor of that group - technically called Providence Children's Friend Society - and inherited its right to nominate patients when it formed in 1949.
The lawsuit says Children's Friend and Service was established in 1834, though under a different name, and is one of the state's oldest existing charitable organizations. It says it helps about 16,000 people a year, providing services including family counseling, crisis intervention and therapy for toddlers with developmental disabilities.
David Caprio, executive director of Children's Friend, said the group discovered paperwork on Lippitt's free bed while combing through its archives several years ago in preparation for its 175th anniversary.
"It was definitely curiosity. It quickly turned to excitement," Caprio said.
The charity sued in November after negotiations stalled over whether the charity had the right to nominate patients to Lippitt's free bed.
Little is known about Lippitt. Court papers say the hospital was raising money at the time by offering permanent free medical beds in exchange for donations of $4,000, and that by 1923 there were 212 such beds.
Other lawsuits have been filed over how hospitals have spent their free bed funds, one of them by the state of Connecticut. That 2003 lawsuit, still pending, alleges that Yale-New Haven Hospital hoarded about $37 million in such funds.
Swirbalus said the charity's case is about access to health care, not money.
Caprio said his group's clients are in especially great need because Rhode Island's budget deficit - estimated at about $550 million - has spurred proposals to reduce the state's subsidized insurance program for the poor.
"It's access to health care for some of the neediest and most vulnerable citizens of Rhode Island," he said. "They're our clients."