It has not been standardized. But for distillation Essential oils contain substances with boiling points up to 200°C or higher so keeping temperature below that is desierable. generally 60 to 160°C is prefered.

Thanks Rohit but my query remains that if dhoomagni is considered in this range what will mandagni remain,Also heat obtained from heating mantle and heat obtained from chulha will also affect the produce. Any suggestion.

Ya definitely you are right Jyoti. When it comes to Mandagni we consider up to 120-250°C, this is specifically in the context of kupipakwa rasayana. As there is no specific standardization available for Dhoomagni you can consider this by keeping your objective of Arka(Distillation ) in minnd