Danbury-based Praxair confirmed that it has reached agreement in principle on the terms of a merger with Linde AG.  The companies would form a new holding company through an all-stock transaction, consistent with the one they announced in December.  The agreement is subject to approval by the Board of Directors of Praxair and the Executive Board and Supervisory Board of Linde.  In a news release, Praxair cautioned that there is no assurance that Board approvals will be obtained.