Harry Potter - Potions Puzzle - Explained

 "Danger lies before you, while safety lies behind, Two of us will help you, whichever you would find, One among us seven will let you move ahead, Another will transport the drinker back instead, Two among our number hold only nettle wine, Three of us are killers, waiting hidden in line. Choose, unless you wish to stay here for evermore, To help you in your choice, we give you these clues four: First, however slyly the poison tries to hide You will always find some on nettle wine's left side; Second, different are those who stand at either end, But if you would move onwards neither is your friend; Third, as you see clearly, all are different size, Neither dwarf nor giant holds death in their insides; Fourth, the second left and the second on the right Are twins once you taste them, though different at first sight."

Ever since 2011 when I first researched information about the Potions Puzzle which is the obstacle that the trio (minus Ronald Weasley) must face in the second to last of the Underground Chambers of the Third-floor corridor in the first book of the series, I have always found it to be rather fascinating.

It wasn't until 2011 that I was able to find out which potion was which, but that's only because I didn't see any images of the Potions Puzzle until I read the information on this page. That cleared up the mystery for me. Even if there wasn't a list telling me the order of the potion lineup, I probably would have figured it out with which was on the page at the time. Or maybe not, since the sizes of the bottles were drawn rather inaccurately.

In that image, the bottle that is supposed to contain the potion to safely traverse the black flames is drawn to be taller than all of the other bottles, except for the first bottle containing the nettle wine. It is inaccurate since the book's description says that the bottle containing the black fire potion is smallest bottle of the lineup.

The picture was later replaced with which depicts the sizes of the bottles more accurately. Except that the first bottle containing the nettle wine is no longer the largest bottle. Instead the second bottle containing the nettle wine is. But enough of that. It's about time I got around to explaining how to work out the mystery of the riddle set up by Severus Snape, but first I'll list the lineup of the bottles.


 * Potion Lineup :


 * 1) Poison
 * 2) Nettle Wine
 * 3) Black Fire Potion
 * 4) Poison


 * 1) Poison
 * 2) Nettle Wine
 * 3) Purple Fire Potion

One of the poisons in the lineup is Weedosoros. It is hinted in one of the earlier revisions of the Underground Chambers page on the Harry Potter Wiki that the third bottle containing poison is the Weedosoros.

The riddle says that the second potion on the left and the second potion on the right are twins once you taste them, though different at first sight. It would have been highly unlikely for those bottles to contain poison. Because if they did, then you probably wouldn't have been able to taste them both to find that they tasted the same.
 * Bottle 1

Since we know that only one potion in the lineup will allow the drinker to safely traverse the black flames, and since we know that only one potion will allow passage back through the purple flames, that implies that neither the second potion on the left nor the second potion on the right contain either of those potions. So therefore they must be the bottles containing the nettle wine.

Since this bottle is neither the smallest or largest bottle in the lineup, and since the bottle directly on the right hand side of this bottle contains nettle wine, then this is obviously one of the three bottles that contain poison, since the riddle says that you will always find poison on nettle wine's left side. The riddle says that while this potion is different from the potion on the far right in the lineup, neither bottle contain the black fire potion.

The riddle says that this potion which is the second potion on the left and the second potion on the right are twins once you taste them, though different at first sight. It would have been highly unlikely for these bottles to contain poison. Because if they did, then you probably wouldn't have been able to taste them both to find that they tasted the same.
 * Bottle 2

In one illustration, this bottle is the largest bottle in the lineup, so if we go by that illustration, that also implies that this bottle doesn't contain poison. Since the riddle says that neither dwarf nor giant holds death in their insides.

Since we know that only one potion in the lineup will allow the drinker to safely traverse the black flames, and since we know that only one potion will allow passage back through the purple flames, that implies that this bottle and its twin do not contain either of those potions. So therefore this bottle and its twin must be the bottles containing the nettle wine.

The riddle says that neither dwarf nor giant holds death in their insides. And since this is the smallest bottle of the lineup, this cannot be one of the three bottle that contain poison.
 * Bottle 3

Since we know that the second potion on the left and the second potion on the right are twins once you taste them, we know that neither of those bottles contain the potion that will allow the drinker to safely traverse the black flames, or the potion that will allow passage back through the purple flames.

Since we know that neither the potion on the left nor the potion on the right contain the potion that will allow the drinker to safely traverse the black flames, then the only remaining bottle in the lineup that could contain that potion is this one.

The riddle says that the second potion on the left and the second potion on the right are twins once you taste them, though different at first sight. It would have been highly unlikely for those bottles to contain poison. Because if they did, then you probably wouldn't have been able to taste them both to find that they tasted the same.
 * Bottle 4

Since we know that only one potion in the lineup will allow the drinker to safely traverse the black flames, and since we know that only one potion will allow passage back through the purple flames, that implies that neither the second potion on the left nor the second potion on the right contain either of those potions. So therefore they must be the bottles containing the nettle wine.

Since this bottle is neither the smallest or largest bottle in the lineup, and since the bottle on the far right in the lineup doesn't contain poison, as it is not on the left side of either of the bottles of nettle wine, then the only remaining bottle in the lineup aside from the bottle on the far left, and the bottle directly on the right hand side of this bottle that could contain poison would be this very bottle.

The riddle says that the second potion on the left and the second potion on the right are twins once you taste them, though different at first sight. It would have been highly unlikely for those bottles to contain poison. Because if they did, then you probably wouldn't have been able to taste them both to find that they tasted the same.
 * Bottle 5

Since we know that only one potion in the lineup will allow the drinker to safely traverse the black flames, and since we know that only one potion will allow passage back through the purple flames, that implies that neither the second potion on the left nor the second potion on the right contain either of those potions. So therefore they must be the bottles containing the nettle wine.

Since this bottle is neither the smallest or largest bottle in the lineup, and since the bottle directly on the right hand side of this bottle contains nettle wine, then this is obviously one of the three bottles that contain poison, since the riddle says that you will always find poison on nettle wine's left side.

The riddle says that the second potion on the left and this potion which is the second on the right are twins once you taste them, though different at first sight. It would have been highly unlikely for these bottles to contain poison. Because if they did, then you probably wouldn't have been able to taste them both to find that they tasted the same.
 * Bottle 6

In one illustration, this bottle is the largest bottle in the lineup, so if we go by that illustration, that also implies that this bottle doesn't contain poison. Since the riddle says that neither dwarf nor giant holds death in their insides.

Since we know that only one potion in the lineup will allow the drinker to safely traverse the black flames, and since we know that only one potion will allow passage back through the purple flames, that implies that this bottle and its twin do not contain either of those potions. So therefore this bottle and its twin must be the bottles containing the nettle wine.

The riddle says that the second potion on the left and the second potion on the right are twins once you taste them, though different at first sight. It would have been highly unlikely for those bottles to contain poison. Because if they did, then you probably wouldn't have been able to taste them both to find that they tasted the same.
 * Bottle 7

Since we know that only one potion in the lineup will allow the drinker to safely traverse the black flames, and since we know that only one potion will allow passage back through the purple flames, that implies that neither the second potion on the left nor the second potion on the right contain either of those potions. So therefore they must be the bottles containing the nettle wine.

Since this bottle isn't found on nettle wine's left side, we know that it does not contain poison. And since neither this bottle nor the bottle on the far left in the lineup contain the black fire potion, then this bottle must contain the potion to allow passage back through the purple flames.