The above mentioned mix isn't Teargas (Often denoted as CN or CS) per se, but a close approximation of pepper spray, based on OC Oleoresencapsaicin.

The stuff in peppers that makes them hot? Thats Capsaicin. The more of it in a substance, the more effect it has. OC is a form of this, purified and mixed into a carrier. A possible OC spray could be synthesised as follows:

DON'T TRY THIS AT HOME, FOR ENTERTAINMENT PURPOSES ONLY

Pick up some sort of hellishly hot sauce, the kind with a warning label, such as Blair's or Dave's Insanity Sauce. Mix it with some canola oil, place into a small squirt gun or bottle. Protect the bloody thing from leaking. An absolutely hellish time for anybody who attacks you and gets this in the face.

ONCE AGAIN, DON'T TRY THIS AT HOME KIDS,THIS EXPERIMENT WAS DONE ONCE ONLY BY PROFESSIONAL IDIOTS