So, I tried to add a 'bottle of milk' to the game. I first added a new liquid to material.dat and defined it in define.dat and then I added the liquid in the following code:

potion /* materialcontainer-> */
{
  DefaultSize = 30;
  Possibility = 800;
  WeaponCategory = BLUNT_WEAPONS;
  Category = POTION;
  DefaultMainVolume = 60;
  DefaultSecondaryVolume = 1000;
  StrengthModifier = 50;
  BitmapPos = 0, 160;
  FormModifier = 25;
  NameSingular = "bottle";
  MainMaterialConfig == GLASS;
  SecondaryMaterialConfig = { 12, WATER, MILK, HEALING_LIQUID, OMMEL_URINE, POISON_LIQUID, VALDEMAR, ANTIDOTE_LIQUID, VODKA, TROLL_BLOOD, OMMEL_SWEAT, OMMEL_TEARS, SULPHURIC_ACID; }
  MaterialConfigChances = { 12, 100, 55, 75, 5, 50, 1, 10, 5, 25, 5, 5, 25; }
  Alias = { 2, "potion", "drink"; }
  Roundness = 70;
  CanBeBroken = true;
  AttachedGod = NONE;
  WieldedBitmapPos = 176, 144;
  IsValuable = false;
  TeleportPriority = 200;
}

The milk is actually working ingame, but for some reason the material last in line (sulphuric acid) isn't ingame anymore, I tried wishing a bottle of sulphuric acid and it doesn't recognize the item.

So, what's going on here?