There are 788 in Webster's Second International. Here's a small sample:
grep -xE '([^e]*e){3}[^e]*' /usr/share/dict/words |grep ^........$
abeltree
Aberdeen
abietene
absentee
Acemetae
acheweed
aesthete
aethered
affeerer
aftereye
agueweed
aiseweed
Alberene
antecede
appellee
arrestee
assessee
axletree
ayegreen
Baedeker
bargeese
beanweed
beaupere
beavered
bebelted
bebreech
bedeafen
beebread
beefhead
beefless
beehouse
beetrave
beferned
befetter
befezzed
begetter
begrease
beheader
behearse
saddists
delegate
needless
nuttiest, fattiest
spinning
The 8-letter word for mixing liquids is "blending," and the 3-letter word is "mix." Both terms refer to the process of combining different liquids to create a uniform mixture.
A triangle.
anaconda, bandanas
manatees
humanhey
Some eight letter words that have three Es are:absenteeattendeecarefreedetaineeedgewiseelectiveembezzleemployeeenvelopeetherealexigenceexpediteforeseenfreebasehoneybeekeepsakelicenseepedigreepeepholeprotegeerefreezereparteesqueegeesteerage
Armchair is an 8 letter word. The 7th letter is i.