what is the importance of Benzophenone in distillation [closed]








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when we realize a distillation of solvent we use benzophenone , 


what is the importance of this latter , Is is considered as an initiator of this operation, that's true ?




Ethereal solvents are often distilled from metals such as sodium In the presence of benzophenone as an indicator. 


When the still is good, the benzophenone is blue/purple, when it goes yellow/brown the still is bad. 


Classically we thought that the colour was related to moisture (ie. A purple colour indicated dryness) however its now generally agreed that the colour is to do with the absence of oxygen rather than moisture. 


The distillation can be done without this indicator, indeed short path distillation almost never uses indicators. The benzoophenone is just useful in recycling stills as it allows one to see when th still needs attention. 


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