This is a question that will combine your knowledge of food, chemistry, and beer.
Spiciness is measured in Scoville Units. Basically:
In Scoville's method, an alcohol extract of the capsaicin oil from a measured amount of dried pepper is added incrementally to a solution of sugar in water until the "heat" is just detectable by a panel of (usually five) tasters; the degree of dilution gives its measure on the Scoville scale. Thus a sweet pepper or a bell pepper, containing no capsaicin at all, has a Scoville rating of zero, meaning no heat detectable. The hottest chilis, such as habaneros and nagas, have a rating of 200,000 or more, indicating that their extract must be diluted over 200,000 times before the capsaicin presence is undetectable. The greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity. Tasters taste only one sample per session.one sample per session.
I'm making a chili beer, and while I have an idea of what I want to do, I thought some math could come in handy. How would you take the Scoville units of, say, a habanero (200,000 units), and the volume of a batch (5 gallons), and figure out how much habanero to add to get the final beer to, say, 75,000 Scoville units?