DR THOMAS R. FRASER ON STROPHANTHUS HISPIDUS. 1009 



It is, however, extremely difficult to separate the crystals from adhering impurities 

 by the use of any solvents ; and even when that is accomplished, the great solubility of 

 strophanthin in water and in rectified spirit, entails much loss, if separation by repeated 

 crystallisation be attempted. The crystalline products obtained when ether is added to a 

 very dilute alcoholic solution of the extract, and when ether is added to a strong solution 

 of the alcoholic extract in water, also both represent nearly pure forms of strophanthin ; but, 

 on several times repeating each process, it was found that sometimes only did it succeed 

 in yielding a crystalline product, while, frequently, it failed to do so. Nice adjustments, 

 extremely difficult to determine, are obviously required of the proportional quantities of 

 active principle, water, alcohol and ether, and of active principle, water and ether, 

 respectively, in order to ensure the separation of the active principle in the form of 

 colourless crystals. 



It was therefore found necessary to devise some other process. In the first place, at 

 an early stage in the research, the removal of impurities and the isolation of the active 

 principle by subacetate of lead was attempted ; as it had been found that after the removal 

 of the copious precipitate formed in solutions of the extract by subacetate of lead an 

 intensely bitter, clear, and only slightly coloured nitrate, of great pharmacological activity, 

 was obtained. When, however, sulphuretted hydrogen was passed through this filtrate, 

 in order to precipitate lead, the active principle was necessarily subjected to the action 

 both of sulphuretted hydrogen and of free acetic acid; and accordingly it was decomposed, 

 glucose appeared in the solution, and strophanthidin crystallised out in great abundance. 

 As the extract obtained by small quantities of rectified spirit from the seeds previously 

 percolated with ether, appeared to consist chiefly of active principle, the removal of the 

 inconsiderable quantity of impurity present in it was attempted by treatment with pure 

 animal charcoal ; but this process also proved unsatisfactory both in the quantity and 

 quality of the product obtained. 



After several other attempts, the following was adopted as a tolerably satisfactory, 

 though, no doubt at the same time laborious, process for separating the active principle 

 in a pure form. 



The active principle was precipitated by a solution of tannin from a strong solution 

 of the extract in water ; the well-washed tannate was thoroughly mixed with recently 

 precipitated, carefully washed, and moist oxide of lead, which was added in the quantity 

 calculated to be necessary for the conversion of the tannin into tannate of lead ; the 

 mixture was digested for several days at a low temperature; and, after it had been dried, 

 it was thoroughly exhausted with rectified spirit, and occasionally with proof spirit. If 

 the alcoholic solution still contained any tannin, as it usually did, it was evaporated to a 

 syrupy consistence, and again treated as above with a smaller quantity of oxide of lead. 

 It was frequently necessary to adopt a third such treatment before every trace of tannin 

 had been removed. The product was now dissolved in weak alcohol, and, if necessary, 

 decanted and filtered from sediment; and through the clear and usually almost colourless 

 solution, a gentle stream of well-washed carbonic acid was passed for two or three days, 



