I'm trying to make an etching solution for copper (PCB) with easy to access materials. I'm using hydrochloric acid (9%), peroxide (common "oxygene" that contains many more ingredients), table vinegar, table sea salt, and bicarbonate soda. Now the recipe mentioned only hydrochloric acid and the peroxide, but it mentioned a hydrochloric acid with high concetrantion (31%). My solution with (the easily accessible) 9% hydrochloric acid didn't worked so I added the other elements and it worked fine. The problem is that I don't know what I'm doing, and what elements causes the reaction. I start with the hydrochloric acid, I put some peroxide inside. Alone it does nothing to the copper. I then add some vinegar, salt, and soda (I suppose soda helps to get oxygen inside the solution) and after a while the reaction starts and it works really quick. (the 5x5 cm copper piece gets dissolved as I like in around 5 minutes. (and whatever I have painted on it with my permanent marker remains).
So can someone explain me what reactions take place, and perhaps which is the crucial material and which I may omit?
Also when I work with that stuff my nose gets irritated, how harmful is this solution and how I may dispose it safely?