There are no “chemical weapons” that cause “burned bodies”. Mustard and Lewisite cause severe blisters, not burns. The difference is immediately obvious. The organophosphorous nerve agents (Tabun, Sarin, Soman, VX and their various analogues) kill through inhibition of acetylcholinesterase, leading in most cases to respiratory failure. Older agents like the “blood agents” (e.g., cyanogen chloride, hydrogen cyanide) also cause respiratory failure. Vomiting agents (e.g., Adamsite) and lachrymatory agents (CS or “tear gas”) usually don’t kill at all.
My gut feel is that we are talking about white phosphorous, i.e. artillery smoke projectiles. That is definitely the sort of thing that would be used in battle, and phosphorous does cause horrific burns. However, while “chemical” in nature, they are not CW because the definition of CW according to Article II of the Chemical Weapons Convention exempts toxic chemicals that are used for military purposes not connected with their toxic properties. In other words, because WP smoke rounds are used for producing smoke rather than poisoning people (which would be very, very hard to do with a unitary shell containing a solid mass of phosphorous), they are not deemed CW. This may sound like a distinction without a difference, but take the example of dimethyl hydrazine, an extremely toxic rocket fuel – if you’re not using it to poison people, it’s not a CW.
The CWC allows for “investigations of allegations of use of CW”, but the allegation has to be levied by a state. Unless a state accuses Turkey of using CW, the OPCW can’t act. If it does act, the allegedly affected human remains will have to be examined. There are obvious and highly distinctive environmental and biological markers for blister and nerve agents; if they were used, the use will be discovered.
