1006 DR THOMAS R. FRASER ON STROPHANTHUS HISPIDUS. 



found, on estimation with Fehling's reagent, to contain 23'4 per cent, of glucose. (Table 

 X. Analysis No. 16.) 



In another experiment with the same strength of solution of extract and of sulphuric 

 acid, but in which the acidulated solution was at once boiled for half an hour, an abundant 

 formation of large and only slightly coloured crystals occurred while the solution was 

 being raised to the boiling point, and before the temperature of 180° F. had been attained; 

 and, at the same time, a peculiar odour, like that of cooked raisins, was developed. The 

 crystals became broken and more deeply coloured by the boiling ; but still, when dried, 

 they weighed 27 '4 per cent, of the extract. The glucose produced amounted to 27 '9 per 

 cent. (Table X. Analysis No. 17.) 



In an experiment in which 0*32 per cent, of sulphuric acid was used, on raising the 

 temperature to 170° F., the solution became opalescent ; but after it had cooled, only an 

 amorphous sediment, amounting to 6*3 per cent, was deposited. When, however, the 

 filtered solution was made slightly alkaline with sodium carbonate, a precipitate, consisting 

 of minute and perfectly formed crystals, was thrown down, which amounted to 13 '7 per 

 cent, of extract. 21 per cent, of glucose was produced. (Table X. Analysis No. 20.) 



In another experiment, where all the conditions were the same as in the preceding 

 one, except that the percentage of sulphuric acid was 1*6 instead of 0*32, no crystalline 

 strophanthidin was produced, but merely an amorphous brown substance, which weighed 

 9 per cent. The quantity of glucose formed was exactly the same as in the preceding 

 experiment, namely. 21 per cent. (Table X. Analysis No. 21.) 



The production in the cold as well as at an elevated temperature of crystalline strophan- 

 thidin and glucose was observed with other acids, and with different degrees of acidity. 

 In many of the experiments, the acidulated solution was left at the ordinary temperature 

 for several days, and then decanted from any crystals that had formed ; and the decanted 

 solution, after having been filtered, was divided into two equal parts, in one of which the 

 glucose was at once estimated, while in the other this estimation was not made until the 

 solution had been boiled for half an hour. By this plan, the production or non-production 

 of crystalline strophanthidin and of glucose in the cold, and of glucose at a temperature 

 of 212° F., and the quantity of each substance produced in these conditions could be 

 ascertained. Even when made with the same acid, the various experiments are not, how- 

 ever, always comparable, as the percentage of acid and of extract in the solutions, the 

 duration of contact, the temperature to which the solutions was subjected, and even the 

 extracts used, were not the same, but, indeed, were intentionally varied. 



In estimating the quantity of glucose by Fehling's reagent, a difficulty was encoun- 

 tered, due to the absence of a sharp indication of the point when the whole of the reagent 

 had been reduced. The disappearance of the blue colour, on which reliance generally is 

 placed, is masked by the production of a greenish-blue, which, on further additions of the 

 glucose solution, gradually passes into distinct green, yellowish-green, yellow, and reddish- 

 yellow. Control experiments appeared to show that complete reduction of Fehling's reagent 

 is not produced until a reddish -yellow colour has appeared, but the shades of colour pass 



