Richard Guthrie, formerly project leader of the Chemical and Biological Warfare Project of the Stockholm International Peace Research Institute, who said he had not seen the original report, said the Russian statement on the makeup of the sarin found outside Aleppo, which the Russians said indicated it was not military grade, might reflect only that "there are a lot of different ways to make sarin."
He added: "The messy mix described by the Russians might also be the result of an old sarin stock being used. Sarin degrades (the molecules break up) over time and this would explain a dirty mix."
But he also said that there could be doubts about the Russian conclusion that the rockets that delivered the sarin in the March 19 incident were not likely to have come from Syrian military stocks because of the use of RDX, an explosive that is also known as hexogen and T4.
"Militaries don't tend to use it because it's too expensive," Guthrie said. He added in a later email, however, that it's not inconceivable that the Syrian military would use RDX "iff the government side was developing a semi-improvised short-range rocket" and "if there happened to be a stock available."
"While I would agree that it would be unlikely for a traditional, well-planned short-range rocket development programme to use RDX in that role, it is not beyond the realms of possibility that, as the Syrian government did not seem to have an earlier short-range rocket programme, it may have been developing rockets with some haste and so using materials that are at hand," he said.