Denatonium
Denatonium, usually available as denatonium benzoate (under trade names such as Denatrol, BITTERANT-b, BITTER+PLUS, Bitrex or Aversion) and as denatonium saccharide (BITTERANT-s), is the most bitter chemical compound known, with bitterness thresholds of 0.05 ppm for the benzoate and 0.01 ppm for the saccharide. 
It was discovered in 1958 during research on local anesthetics by MacFarlan Smith of Edinburgh, Scotland, and registered under the trademark "Bitrex". 

Dilutions of as little as 10 ppm are unbearably bitter to most humans. Denatonium salts are usually colorless and odorless solids but are often traded as solutions. They are used as aversive agents (bitterants) to prevent inappropriate ingestion. Denatonium is used in denatured alcohol, antifreeze, preventive nail biting preparations, respirator mask fit-testing, animal repellents, liquid soaps, shampoos, and Nintendo Switch game cards to prevent accidental swallowing or choking by children. It is not known to pose any long-term health risks.

The name "denatonium" reflects the substance's primary use as a denaturant and its chemical nature as a cation, hence the New Latin suffix "-onium".
Q1417728
trade name
Concept
None
bitter
UNK
Q11173
chemical compound
Concept
Q1868462
local anesthetic
Concept
Q6721885
MacFarlan Smith
ORG
Q23436
Edinburgh
LOC
Q22
Scotland
LOC
None
ppm
UNK
Q4828343
aversive agent
Concept
Q4919044
bitterant
Concept
Q213449
ingestion
Concept
Q855523
denatured alcohol
Concept
Q503288
antifreeze
Concept
Q1367423
nail biting
Concept
Q271779
respirator
Concept
Q4438192
fit-testing
UNK
Q14535662
animal repellent
Concept
Q34396
liquid soaps
Concept
Q180204
shampoo
Concept
Q1199815
Nintendo Switch game cards
Concept
Q2185118
denaturant
UNK
Q36496
cation
Concept
Q1248221
New Latin
Concept
Q102047
suffix
Concept
Q414815
Denatonium
Concept
Q414815
Denatonium
Concept
Q414815
Denatonium
Concept
1958-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1958
DATE
+0.05^^http://www.w3.org/2001/XMLSchema#decimal
0.05
NUMBER
+0.01^^http://www.w3.org/2001/XMLSchema#decimal
0.01
NUMBER
+10^^http://www.w3.org/2001/XMLSchema#decimal
10
NUMBER
instance of
use
located in the administrative territorial entity