Its in the title but I want to rationalize all of my artificer items with real science, and science that is realistic for the time. So do you think I could make dry ice, if so how?

You could use it as fluff for dealing cold damage, but D&D worlds don't work under real-world physics: stuff is comprised of mixtures of the Four Classical Elements, not the Periodic Table of the Elements.

If you have the para- or quasi- or whatever- elemental plane of ice in your cosmology, the ice from there might well be "dry", in the sense that it doesn't melt into water.

In game the way you do this is design a new spell.   No reason at all to try and make it using existing spells.

I though about that but I can't think a way to compress the gas enough, I needed this to condense Acetylene as fuel for my flamethrower spear(I totally forgot to mention in the original post). If I'm just compressing gas then I run into the same problem as making dry ice, I can't find a way to get it cold enough, or the pressure high enough for it to condense.

Edit: This was a response to ArntItheBest, I've never used the thread feature before and though it would automatically set who you were responding to.

Edit2: Just for convenience sake, Acetylene can only exist as a liquid above 1.27atm (18.66385psi) with a temp less than -80.8C(-177.44F). :)

Yeah, the Reply button notifies the person that you're replying to that there was a reply to their post (while everyone else who's posted just gets a notification of a new post) but it doesn't tell that person which post is being replied to.  It's much better to use the quote button instead if you're addressing a specific post.

Getting back to the question at hand, there are no mechanics for that level of detail in D&D.  You don't need to provide a working blueprint for a design and the game doesn't really let you build steampunk Fallout customized weapons in the first place.  If you really want to have a flamethrower spear, you'll need to work it out with the GM and most likely it would be a magic item, not a spear that you've duct-taped an acetylene torch to.