Octonions form Algebra

Theorem
The set of octonions $\Bbb O$ forms an algebra over the Field of Real Numbers.

This algebra is:
 * $(1): \quad$ An alternative algebra, but not an associative algebra.
 * $(2): \quad$ A normed division algebra.
 * $(3): \quad$ A nicely normed $*$-algebra.

Proof
The octonions $\Bbb O$ are formed by the Cayley-Dickson construction from the quaternions $\Bbb H$.

From Quaternions form Algebra, we have that $\Bbb H$ forms:
 * $(1): \quad$ An associative algebra
 * $(2): \quad$ A normed division algebra
 * $(3): \quad$ A nicely normed $*$-algebra.

From Cayley-Dickson Construction forms a Star-Algebra, $\Bbb O$ is a $*$-algebra.

From Cayley-Dickson Construction from Nicely Normed Algebra is Nicely Normed, $\Bbb O$ is a nicely normed $*$-algebra.

From Nicely Normed Cayley-Dickson Construction from Associative Algebra is Alternative, $\Bbb O$ is an alternative algebra.

Now suppose $\Bbb O$ formed a associative algebra.

Then from Cayley-Dickson Construction from Commutative Associative Algebra is Associative, that would mean $\Bbb H$ is a commutative algebra.

But from Quaternions form Algebra it is explicitly demonstrated that $\Bbb H$ is not a commutative algebra.

So $\Bbb O$ can not be a associative algebra.