Should I titrate NaOH with KHP and HCl with Borax, or titrate NaOH with KHP then HCl with the NaOH?
Yes.
Ok, sorry about that. But I wanted to start off by letting you know that both are acceptable, and required, depending on what method is validated for the application involved. We can't really help you more than that.
The latter sounds like it would be introducing statistical error.
Yes you can insert multiple magnifying statistical errors. Or you can do both perfectly (within experimental error) and get the best results. That's why we validate.
Also is there a better standard to titrate the HCl with than Borax?
The USP specifies tromethamine as the primary standard for volumetric HCl standardization. It may be "better" or it may not be "better." No one who uses standardized HCl to produce a pharmaceutical that will be sold in the United States is permitted to use anything else, unless they validate their new procedure.
A random blog on Google actually suggest using dried sodium carbonate as a standard. WHich gives me a Yikes! moment, but
whatevs:
http://www.pharmaguideline.com/2010/09/preparation-and-standardization-of-1m.htmlTo what standard do you need your answer?