The Film Developing Cookbook altered Vestal's formula by omitting the hydroquinone, increasing metol to 3g and borax to 5. Anchell & Troop published the formula for 1L vs 4. I notice most of the Cookbook's charted formulas state ""cold water to make 1L". In some cases their formula spreadsheets do not identify water volume. Differences most likely are authors variations and the quantity of chemicals to make 1L or 4.
The original source!
Split D-76, From Vestal's book, "The Art Of Photography".
Solution A. (Metric)
Water 3L
Metol 8g
Sulfite 200g
Hydro quinine 20g
Water to make 4L
Solution B
Water 3L
Sulfite 200g
Borax 8g
Water to make 4L
The story behind the formula is Vestal could not recall Paul Faber's published split D-76 formula which uses 2x as much sulfite in solution A, and none in solution B. Not remembering the proportions David Vestal divided the sulfite equally between the two solutions. The advantage is the sulfite helps preserve the developer and is a silver solvent. Time and temperature are not critical with this developer. He claims no loss of film speed and beautiful fine grain, long scale, negatives which cannot be easily overdeveloped.
Fill one film tank with solution A and a second with solution B. In total darkness, place the film reel in solution A. Agitate 10s each minute for about 3 minutes. In total darkness open tank A and move the reel to tank B. Close tank lid, turn on lights, and develop in tank B for about 10 minutes.
Vestal suggested to use the developer as a one shot and to never get solution B into solution A. You can use one film developing tank, pouring the solution in and out with no bad effects.