A thermodynamic analysis of the open‐tube chemical vapor transport of using the reaction of Zn and has been attempted, assuming a simple reaction model for Zn and vapor phase species. Based on this analysis, computer data have been derived to show variation in vapor phase content as a function of temperature, and reactor Zn and concentrations. The range of Zn reactor pressures examined was from 0.00260–0.00013 atm with pressures varying from 10−3–10−3 of these values over a temperature interval of 723°–1473°K. For the range of Zn pressures examined, pressures of 10–100X these values lead to vapor phase concentration curves most amenable to precise experimental control. At pressures 10X those of Zn pressures particularly, high‐temperature plateaus develop where vapor phase Zn content is relatively temperature insensitive and which look promising as transient source sites. Similar plateaus do not exist at lower temperatures where they might have value as temperature insensitive deposition sites.