I don't know if I can effectively convey what I am doing here, but I am going to try because I need the help. I am trying to determine my ratio of acid to base and subsequently make a .5M Tris-HCl buffer utilizing Tris base, and concentrated HCl. By my calculations I get a 19.05 parts acid/1 part base ratio. Using this, I divide the total amount of buffer I am looking to make (200mL) by the total number of parts in solution (20.05 or 19.05+1). Given this, I get ~190mL acid to 10 mL base. Here is where I was a little unsure of myself. To calculate the amount of base I need, I multiplied the MW of Tris-base (121.4 grams/mole) by the molarity of the solution by the number of mL specified above (10mL). To calculate a 190mL of a .5M solution of HCL, I used (C1)(V1)=(C2)(V2), where C1=.5M, V1=.19 Liters, C2=11.6M (molarity of concentrated HCl). From this, I calculated that I needed to add 8.2mL of conc. HCl to 181.8mL dd H20. The final step was to add my acid solution to my base solution. NOW FOR THEMILLION DOLLAR QUESTION! I tested some of this "buffer" on pH paper and got a pH of just above 1.0. Why? The stated pKa value seems to fluxuate between 8.08 and 8.3. I was using 8.08 in application to HH. Any input would be very much appreciated. Thank you.