A delivery system, for delivering a substantially constant number of moles of a liquid precursor compound vapor per unit volume of a carrier gas to a plurality of reactors that are communication with the delivery system; the liquid precursor compound being in a liquid state in a delivery device, said system comprising: a delivery device having an inlet port and an outlet port of the delivery device containing a liquid precursor compound; a first proportional valve; wherein the delivery device is in operative communication with a first proportional valve; wherein the first proportional valve is operative to control the flow of the carrier gas based on an applied voltage, where the first proportional valve is in fluid communication with a first stream that contacts the delivery device; a second proportional valve in fluid communication with a second stream that bypasses the delivery device and contacts the first stream at a point downstream of the delivery device, where both the first stream and the second stream emanate from a single stream; a physical-chemical sensor; the physical-chemical sensor being disposed downstream of the delivery device and being operative to analyze chemical contents of a fluid stream emanating from the delivery device; the physical-chemical sensor being in communication with the first proportional valve; a first pressure/flow controller being in operative communication with the physical-chemical sensor and with the first proportional valve, wherein the delivery system is operative to deliver a substantially constant number of moles of a liquid precursor compound vapor per unit of volume of the carrier gas to a plurality of reactors that are in communication with the delivery system, the liquid precursor compound being in a liquid state in the delivery device; and a pressure sensor, the pressure sensor being disposed downstream of the delivery device and in fluid communication with the delivery device and the second proportional valve and a second pressure/flow controller being in operative communication with the pressure sensor, where the second pressure/flow controller is in electrical communication with the second proportional valve; wherein the physical-chemical sensor along with the first pressure/flow controller, the first proportional valve and the delivery device form a first closed loop that encompasses the first stream; wherein the pressure sensor along with the second pressure/flow controller, the second proportional valve and a mixing chamber form a second closed loop that encompasses a second stream; and wherein said second stream is directed to said mixing chamber where it contacts said fluid stream emanating from the outlet port of the delivery device. a delivery device having an inlet port and an outlet port of the delivery device containing a liquid precursor compound; a first proportional valve; wherein the delivery device is in operative communication with a first proportional valve; wherein the first proportional valve is operative to control the flow of the carrier gas based on an applied voltage, where the first proportional valve is in fluid communication with a first stream that contacts the delivery device; a second proportional valve in fluid communication with a second stream that bypasses the delivery device and contacts the first stream at a point downstream of the delivery device, where both the first stream and the second stream emanate from a single stream; a physical-chemical sensor; the physical-chemical sensor being disposed downstream of the delivery device and being operative to analyze chemical contents of a fluid stream emanating from the delivery device; the physical-chemical sensor being in communication with the first proportional valve; a first pressure/flow controller being in operative communication with the physical-chemical sensor and with the first proportional valve, wherein the delivery system is operative to deliver a substantially constant number of moles of a liquid precursor compound vapor per unit of volume of the carrier gas to a plurality of reactors that are in communication with the delivery system, the liquid precursor compound being in a liquid state in the delivery device; and a pressure sensor, the pressure sensor being disposed downstream of the delivery device and in fluid communication with the delivery device and the second proportional valve and a second pressure/flow controller being in operative communication with the pressure sensor, where the second pressure/flow controller is in electrical communication with the second proportional valve; wherein the physical-chemical sensor along with the first pressure/flow controller, the first proportional valve and the delivery device form a first closed loop that encompasses the first stream; wherein the pressure sensor along with the second pressure/flow controller, the second proportional valve and a mixing chamber form a second closed loop that encompasses a second stream; and wherein said second stream is directed to said mixing chamber where it contacts said fluid stream emanating from the outlet port of the delivery device.