We introduce a new kind of abstract machine based on the chemical metaphor used in the Gamma language of Banatre and Le Métayer. States of a machine are chemical solutions where floating molecules can interact according to reaction rules. Solutions can be stratified by encapsulating subsolutions within membranes that force reactions to occur locally. We illustrate the use of this model by describing the operational semantics of the TCCS and CCS process calculi and of the fragment of Milner, Parrow and Walker's Calculus of Mobile Processes used by Milner to encode the lambda-calculus. We also give ideas on how to extract a higher-order concurrent lambda-calculus out of the basic concepts of the chemical abstract machine.