What is the commonality between the antibiotic arsphenamine and azodye ?

Explanation

To answer the question regarding the commonality between the antibiotic arsphenamine and azodye, we can break down the solution into several steps:

### Step-by-Step Solution:

1. **Understanding the Compounds**:
- **Arsphenamine**: This is an antibiotic that contains arsenic and is used to treat syphilis. Its structure includes an arsenic atom double-bonded to another atom and is connected to a benzene ring.
- **Azodye**: This is a class of dyes characterized by the presence of an azo group (-N=N-), which connects two aromatic rings.

...