And what evidence do you have that the rebels don't have the capability to mix the gas?
You can say the rebels don't have the capacity to do it all you want. The problem is just saying it isn't evidence.
Ah, an adult just walked in, with a reasonable question.
Because, having over 15 years of military experience being trained and dealing with such weapons, the conditions on the battlefield of syria would not allow the rebels or jihadists to be able to perform the mixing and insertion of the mixed toxins into rocket-capable/ launchable canisters, let alone in the quantity needed to devastate an area as large as the two distinct regions of Damascus that were hit. Well over a hundred rockets, each mixed with still-active SG in its liquid state (cold - not room temperature, to prevent its evaporation), then mixed with other ingredients, and then inserted into the rocket-canisters so that it will maintain its integrity after being fired and heated quickly by the rocket and friction. The rebels do not possess the skills, field conditions, equipment, lab environment, refridgeration equipment, quantity of rockets, and mixing tools, on the battlefield, it really is not that hard to understand.
I do not have the expertise, nor do I wish to argue your assertion, but the rebels could have captured several rocket launchers that were loaded and meant to be fired on them.