I am making nitric acid with sodium bisulfate and potassium nitrate. I have a simple distillation setup. The 3 times I have done this reaction, I have gotten mere drops of the stuff. Too low to even calculate the yield.

I have been using
>100g potassium nitrate
>200g sodium bisulfate

I do this dry, melting the sodium bisulfate, with slow stirring. I get loads of brown dioxide gas, and i get vapors condensing on the sides of my flask, but hardly anything comes through the condenser. I have made damn sure all my joints are sealed, so thats not the problem.

The stuff I do get passes the copper test

Any idea why the yield has been so low? Am I fucking stupid?