<PAGE>



                                                                    EXHIBIT 31.1


                CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,
                       AS ADOPTED PURSUANT TO SECTION 302
                       OF THE SARBANES--OXLEY ACT OF 2002


I, A. John Leach, Jr., certify that;

     1)   I have reviewed this annual report on Form 10-K of Covista;

     2)   Based on my knowledge, this annual report does not contain any untrue
          statement of a material fact or omit to state a material fact
          necessary to make the statements made, in light of the circumstances
          under which statements were made, not misleading with respect to the
          period covered by this annual report.

     3)   Based on my knowledge, the financial statements, and other financial
          information included in this annual report, fairly present in all
          material respects the financial condition, results of operations and
          cash flows of Covista as of, and for, the periods presented in this
          annual report.

     4)   The registrant's other certifying officer(s) and I are responsible for
          establishing and maintaining disclosure controls and procedures (as
          defined in Exchange Act Rules 13a-15e and 15d--15e) and internal
          control over financial reporting (as defined in Exchange Act Rules
          13a--15f and 15d--15f) for the registrant and have:

              a)  Designed such disclosure controls and procedures, or caused
                  such disclosure controls and procedures to be designed under
                  our supervision, to ensure that material information relating
                  to Covista, including its consolidated subsidiaries, is made
                  known to us by others within those entities, particularly
                  during the period in which this annual report is being
                  prepared;

              b)  [omitted pursuant to the guidance of Release No. 33-8283
                  (June 5, 2003)];

              c)  Evaluated the effectiveness Covista's disclosure controls and
                  procedures and presented in this report our conclusions about
                  the effectiveness of the disclosure controls and procedures,
                  as of the end of the period covered by this report based on
                  such evaluation; and

              d)  Disclosed in this report any change in Covista's internal
                  control over financial reporting that occurred during
                  Covista's most recent fiscal quarter (Covista's fourth
                  fiscal quarter in the case of an annual report) that has
                  materially affected, or is reasonably likely to materially
                  affect, Covista's internal control over financial reporting;
                  and

     5)   Covista's other certifying officers and I have disclosed, based
          on our most recent evaluation of internal control over financial
          reporting, to Covista's auditors and the audit committee of
          Covista's Board of Directors (or persons performing the equivalent
          functions);

              a)  All significant deficiencies and material weaknesses in the
                  design or operation of internal control over financial
                  reporting which are reasonably likely to adversely affect
                  Covista's ability to record, process, summarize and report
                  financial information; and

              b)  Any fraud, whether or not material, that involves management
                  or other employees who have a significant role in Covista's
                  internal control over financial reporting.


Date: April 29, 2005                   By: /s/ A. John Leach, Jr.
                                           ----------------------------
                                           A. John Leach, Jr.
                                           President and Chief Executive Officer



                                  EXHIBIT 31.1