Was that P30 or P3 chemistry? I still have some P30 kits and just looked at them. No seperate neutralizer. The P30/Cibachrome manual says that all 3 spent solutions when mixed together are nearly neutral and can be poured down the drain with no further treatment.
There was an evolution in chemistry. Way back when, the kit came with neutralizer chemicals that you added before disposing of the stuff. One guy wrote that at the time his darkroom still had metal drain pipes from the sinks, and "even with the neutralizer, it destroyed the pipes in very short order. Just ate through them. Nasty stuff."
Someone else wrote, " Ilford had to reformulate the P-30 chemistry. According to the B&H website they are using a modified version of the P-3. It doesn't use sulfuric acid. They call it kit 3.5 and/or P-3V. It isn't real clear."
Note that 'neutralization' refers to the inherently acid pH characteristic of the solution, and would not have something to do with rendering any carcinogens to be not hazardous to one's health...it only indicated that (in theory) the pipes were less likely to corrode.
P3 was the commercial processor chemistry, the AII was the amateur stuff back in the early 1980s, and the P30/P30P was the renamed chemistry intended for both amateur and commercial use.
Ilford published this comment about the P3 chemistry:
"NEUTRALIZATION Read the handling and safety procedures before working with liquid chemistry. Neutralization is accomplished by adding 16 ounces of sodium bicarbonate (baking soda) for each gallon of used bleach. After the sodium bicarbonate is added the solution will fizz vigorously. Use a container at least twice the volume of the solutions to be neutralized. DO NOT cover the container."
From old B&H information,
Ilford P3V (P-30) (Liquid) Kit for Ilfochrome Paper - 3.5 Liters
B&H # ILP3035LK MFR # 1137758
"Ilford Ilfochrome P3V (P-30) - Ilford is no longer able to produce powder chemistry since Mobberley stopped production. As a quick fix, they have introduced a Kit 3.5 (based on P3 chemistry used in professional labs). With the introduction of the new bottle (with child proofed caps), they will re-introduce a P30 kit in 2-litre size (planned with sulphuric acid but easy to convert to old acid)
"P30 or P30P chemistry used a different type of acid than P3. However, the ready to use solution contains more or less the same ingredients sulphamic acid + p-Toluenesulphonic acid or Sulfuric acid + 7K + Ludigol 100° + KI and Bleach accelerator
"The Bleach of the Kit 3.5 contains about 33% sulfuric acid, which is totally different from the point of view of hazard
"p-Toluenesulfonic acid is an organic compound as a white solid that is soluble in water, alcohols and other polar organic solvents; TsOH is a strong organic acid, about a million times stronger than benzoic acid; It is one of the few strong acids that is solid and, hence, conveniently weighed; Unlike some other strong acids, TsOH alone is non-oxidizing
"From Ilford's experience in developing P30, P3, P3X or P5 processor, the bleach temperature is the critical factor for metallic part corrosion; Therefore, Titanium was recommended for building equipment in contact with sulfuric acid as soon as the temperature exceeds 32°C. "