You can find the 2nd edition of "Principios de Operaciones Unitarias" by Alan S. Foust and colleagues available for online viewing or download through several academic and document-sharing platforms:
The text is uniquely organized by physical phenomena rather than specific equipment, grouping similar operations to emphasize their shared scientific basis: principios de operaciones unitarias alan foust pdf free
The author presents the material in a clear and concise manner, using a combination of theoretical derivations, practical examples, and illustrations to help students understand complex concepts. The text also includes numerous problems and exercises to reinforce learning and promote critical thinking. You can find the 2nd edition of "