Can anybody tell me how to determine the concentration of the nitric acid that I’ve been producing? I use calcium ammonium nitrate with sulfuric acid and water and distill it. The process is supposed to yield a 68% concentration. The byproduct is simple gypsum which can be washed down the drain. I know there’s some type of math calculation by volume or weight but I don’t know how to do that. I thought using a hydrometer in a given amount of 68% nitric acid that I bought from the store and compared that to what I made. There’s a small difference but I don’t know what the difference in percentage is just by reading the hydrometer.