some vague phrases (liquid from the vial was pure alcohol, etc.)

[Klpno]

Hello everyone
I'd like to ask about some unclear things in the following text (extract from SF story). It's about teachers at the party.

Then the drunken man scanned the room. Searching for an escape route? No, he wanted the big bowl set on the central table -- a leather bowl where sweet punch and fermented gig-berries created a small pond.

A few paragraphs further:

"Oh, but it's far worse than that!" His colleague stuck the long straw into his mouth, then slipped the other end into a small wooden flask hidden in his coat pocket. He sucked up the liquid and covered the straw's upper end with his thumb, lifting the leaves until he could see the open punch, then he set the bottom of the straw against the sweet drink. "Of course I mean this as an illustration," he mentioned. Then he winked at the scientist, saying, "I know, I know. There's no geniune consensus among experts. Or should I say specialists? Since there is, if you think about it, an important difference between those two words..."
"Don't," Jopale cautioned.
But the man struck a long match, making a yellow flame. Then winking at his audience, he said, "A little gas here, a lot of gas there. People die, but not too many of us. And maybe we will marshal necessary resouces. Cut holes to the Ocean below and let out the bubbles in manageable little breaths. Or pump pure oxygen down under our feet, freshening the cold dead water." He waved the flame in front of his eyes. "Perhaps human can do whatever it takes, and our atmosphere isn't destroyed when the hydrocarbons eat up our precious free oxygen"
"You're drunk," the scientist complained.
"Wonderfully drunk, yes." Then the teacher of city names and island positions laughed, and he lowered the flame.
Everyone stared at the leaf-covered punch.
Jopale assumed that the liquid from the vial was pure alcohol. But his colleague had decided to make a more effective demonstration of his argument, which was why he used a collection of long-chain hydrocarbons purchased from an industrial source -- a highly flammablle concoction that made a soft but impressive wooshing sound as it set the leaves on fire, and then the drunken man's hand, and a moment later, his astonished, pain-wracked face.

1. Does the phrase "He sucked up the liquid" mean that the liquid from the flask reached his mouth through the straw?

2. ...and covered the straw's upper end with his thumb.
I think that he did this not spontaneously but for certain purpose. But I can't figure out what was his purpose.

3. Is the "vial" the above mentioned wooden flask?

4. Do I understand correctly what happens in the passage: this man added a liquid from his wooden flask to the pond of punch, then he added hydrocarbons there and after that lowered the burning match to the pond which resulted in his hand and face burning?

[Mister Micawber]

.
1. Does the phrase "He sucked up the liquid" mean that the liquid from the flask reached his mouth through the straw? -- Yes

2. ...and covered the straw's upper end with his thumb.
I think that he did this not spontaneously but for certain purpose. But I can't figure out what was his purpose. -- The vacuum created by sucking up the liquid and then sealing the top of the straw keeps the straw filled with the flammable hydrocarbon so that it can be transferred to the punch bowl.

3. Is the "vial" the above mentioned wooden flask?-- Yes

4. Do I understand correctly what happens in the passage: this man added a liquid from his wooden flask to the pond of punch, then he added hydrocarbons there and after that lowered the burning match to the pond which resulted in his hand and face burning?-- Yes, but the liquid is the hydrocarbons.
.
_________________
Native English teacher at Mister Micawber's

[Klpno]

Thank you very much, Mister Micawber!!!