Choosing the correct amount of reflux for a column requires a balance between two primary factors, the purity of the tops product and the operating costs of running with a high reflux ratio. To obtain the desired purity in the tops product adequate reflux is required to allow rectification to take place in the rectifying section of the column (top portion above feed plate). Decreasing reflux increases the number of plates required to achieve the same separation. The minimum reflux ratio is obtained from the case of a column with an infinite number of plates