It might seem macabre to some but right-to-die campaigner Philip Nitschke says it's all in the name of science.

The founder of Exit International wants to be sure that a cheap and readily available substance that's fast emerging as a new choice for elected deaths actually delivers a peaceful ending.

Dr Nitschke says two Australians, both from Brisbane, used the substance to die in May.

Both chose to privately stream their deaths to him, so he could see if it did, indeed, provide a good and timely death.

Dr Nitschke says two other Australians have promised to do the same, and he hopes there'll be others who follow suit.

The former GP says a lot is known about how the predominant euthanasia drug Nembutal works.

But the same can't be said of the new substance which is a fraction of the cost, and unlike Nembutal, can be readily and legally obtained.

"This is all very new," Dr Nitschke told AAP.

"Some people who have been planning to take this step have been very generous. They do not mind having their deaths observed because they are aware that we are very keen to get good information."

He said initial experiences with the substance indicate it could be a promising alternative to Nembutal, which users must illegally import from overseas.

"These substances are available and they are legal, you don't need to be approved, and you don't need a prescription. You are not doing anything illegal to obtain it."

Australian Associated Press