You can't proceed without the manual. This was Sierra's form of copy protection.
Al Lowe (the game's creator) has the text of the manual up on his site: http://www.allowe.com/FPFP/manual.htm
I've also downloaded it in PDF form but I don't remember where I downloaded it from.
I can't remember exactly, but I think to get some amounts you need to pour some in and then pour a smaller amount out. I think it has to do with the size of the vials you use. It's been a long time though, so I'm not positive.