What chemical to clean clogged inkjet printhead?

[Gew]

I can't remove the printer head on my cheap HP 2720e (I think) but the issue is not the head but the cartridge, I have an old dried one that yesterday wouldn't print black at all, whilst shifting to a non dried cartridge makes beautiful prints. So, the issue is not in the head thingie but in the cartridge. That said, I boiled a pot of water and threw the cartridge in there for ~15 minutes or so. After taking it out and shaking it I suddenly heard the ink squawping around in there, so I think I did something good. Now, with the cartridge put inside, it does print black, but like ½ of the rows are missing. So it feels that I'm stuck within arms reach to the finish (victory!) line, sad life. What would my next step be? I'm thinking about buying 1l of white spirit (the shit you use to dissolve paint) and pouring it in i glass and put the cartdrige in there. Or is this bad practice?