4% solution of nitro - cellulose in a mixture of alcohol and ether is called 

• Collodion is a flammable syrup solution that is often used for surgical dressing. This solution contains nitrocellulose in a mixture of alcohol and ether. 
• The amount of nitrocellulose in the syrup solution is precisely 4%, which is called pyroxylin. 

Therefore, option (C) is correct.