Four of the children were taken to hospital.
The Queensland Ambulance Service’s Peter Batt said the substance was later discovered to be Mystical Fire, a copper-based product which can be used to colour the flames of wood-burning fires.
He said the children would make a complete recovery.
“They’ll be fine. It was only taken in small quantities,” he said.
“The most serious [effects] we can expect is vomiting and upset tummies.
“The chemicals can cause inflammation in the mouth but none of the children exhibited any signs of that.”
Mr Batt said some children had mistaken the product for lollies.
One mother said her nine-year-old son turned down what he was told was a lolly from a classmate.
“He said he didn’t want it and walked away,” she said.
“I cried. I feel sorry for the kids. I was crying. I can feel what they feel.”
Two children were taken in a stable condition to Redcliffe Hospital, and another two were taken to Prince Charles Hospital in Brisbane for further treatment.
A Queensland Department of Education spokesman said the school followed correct procedure in calling paramedics.
“The principal is investigating the cause of the incident and if necessary, will take appropriate disciplinary action,” the spokesman said.