I can't get to my refernces right now, so this comment will be somewhat incomplete. Sodium sulfate is usually added to developers used at high temperatures to even out the penetration into the emulsion. Even so, development times remain uncomfortably short with many developers. Diluting the developer will increase the developing time, but it also decreases the contrast. Some tropical developers, such as Agfa 16 and 64, Gevaert G.222a and G.223, and Kodak D-13 and DK-15, are around, but most have become obsolete. I have used D-76 at up to 27C without undue problems, but above that is unknown territory. Here is the formula for G.222a. It is an example of the use of sulfate to get good high temperature performance.

Gevaert G.222a Tropical film developer

Water (125F/52C) 750 ml
Metol 2 g
Sodium sulfite (anh) 50 g
Hydroquinone 5 g
Sodium sulfate (anh) 45 g
Sodium carbonate (anh) 30 g
Potassium bromide 1.5 g
Cold water to make 1 l

Mixing instructions: Add chemicals in specified sequence.
Dilution: Use undiluted
Starting point development time: 2 mins. (86F/30C)

Ref: Digitaltruth.com