Can't jump up to broken staircase in Lab.

[SunshineDragon]

Hello friends, I'm having a great deal of trouble doing a seemingly simple thing. I've gotten my jar of chemicals and I'm ready to dissolve that icky red stuff, but I can't seem to get out of the lab. No matter how I position the crate or how close I come to the right hand side piece of wood while jumping, I can't seem to get up and out. I've scoured the Mac walkthrough and I can't find any hints to help. I'd love some pointers if you got 'em! Thank you!