PENICILLIN as a chemotherapeutic agent is usually employed in the form of its sodium or calcium salt: a concentrated solution of one of these salts is used for parenteral injection or for local application. For the latter form of treatment penicillin in solid form is often used (usually the calcium salt). Owing to the instability of solutions of these salts of penicillin it is necessary to prepare and store the salts in the solid form and to dissolve in the appropriate volume of water or saline shortly before required.