Several distillation variations are used in the organic laboratory depending on the properties of the mixture to be purified. The apparatus in Figure 5.1 is used to perform a simple distillation and is used if the components have widely different boiling points (greater than a 100 °C difference in boiling points). If a simple distillation is attempted on a mixture where the components have more similar boiling points (less than a 100 °C difference in boiling points), it will fail to purify the mixture completely. Instead, fractional distillation can be used to improve the chances of purification. Vacuum distillation may be used when the boiling points of the mixture's components are very high (>150 °C), or steam distillation if the components are very water insoluble. The distillation variations are summarized in Table 5.1, and are discussed in detail in this chapter.