During WWI? Yes, the Ottomans did use chemical weapons although... I'll have to look it up and edit this post later, I know what instance I'm thinking about but it was a one time thing, be surprised if I can even find it on the internet.
Edit:
La Renaissance was a French language newspaper based in Constantinople in 1918-1920. It was of course all news that concerned Armenians. It was either printed for propaganda purposes, or to counter any censorship but it should be noted that decades later survivors and others would confirm the paper's daily reports. It's also very important to modern historians as it covered the postwar trials and is good for cross-referencing.
Now, during the third session of the Trabzon trials it was brought to light by doctors that in two schools, gas, and gas equipment, was used on school children. This was covered in an article which is sourced by well known authors in dozens of books, and if you could find it I'm sure it will detail this part of the trial. You might even find what gas was used and who ordered it.
