The Chemistry of Anaesthetics, IV: Chloroform.

Abstract

C. is open t o objection for two reasons: first, the resins turn brown a t this temperature and undoubtedly there is some change in composition; second, a constant weight cannot be obtained. When the resins are dried in vacuo there is no evidence of much change in composition and when. completely dried there is practically no change in weight. Great care should be taken in securing petrolic ether of suitable quality for the extraction of the soft resins. The practice in this laboratory is bo make two distillations, starting with the commercial product sold by dealers (boiling point 40-60') and each time taking the fraction distilling over under 45 O C. Acknowledgment is due Mr. B. Pilkington for valuable assistance given in making some of the analytical determinations given in this paper. CONCLUSIONS. I. A comparative study has been made of some of the present methods used for the determination of hard and soft resins in the hop and their defects pointed out. 2. A method has been proposed by the authors which they believe overcomes some of the objections to present methods.