Tris is a common buffering agent and is short for tris[hydroxymethyl]aminomethane (C4H11NO3, 2-Amino-2-hydroxymethyl-propane-1,3-diol).
- The formula weight is 121.14
- The pKa of Tris is 8.3
- dpKa/dT is -.028
- A buffer at pH 6.8 at 25°C will have a pH of 6.46 at 37°C
- Note that adding HCl during titration will affect the temperature of the solution
- Dilution by a factor of 10 will reduce the pH by 0.1 pH units.
Preparing a 1M Tris, pH 7.4 solution, from biologicalworld
- Weigh 121.1 g Tris in 700 ml double distilled water
- Do not start with too much water; otherwise, the volume after pHing may be too great
- Start stirring, and then check the pH
- With a 3M HCl solution, start to pH the solution such that the pH reaches 7.4
(Be careful not to inhale the HCl.)
- Add with double distilled water up to 1L
- Filter or autoclave if necessary
- May be better to store at 4 degrees C
- Dilute to appropriate concentration for use in biochemistry or molecular biology experiments. 20 mM or 50 mM Tris, pH 7.4 solutions are common.
- 18 months for Tris-HCl buffer according to this data sheet 
- 2 years for Tris-EDTA according to this data sheet