Dr. Hancock on Quinine. 317 



Sj of bark* was infused in 8 oz. of hot water, with 3'ii of diluted 

 sulphuric acid. This had scarcely any sourness, or not more 

 than water with half the proportion of acid. The infusion 

 had, however, a strong taste and odour of the genuine cinchona. 

 In a subsequent experiment not the smallest separation or 

 change of appearance was' caused by adding the sulphuric acid 

 to the infusion previously filtered, nor, on the following day, 

 had the least change ensued. 



The infusion of caramacata (a bitter febrifuge bark of the 

 Orinoko) also takes off the acid taste of the sulphuric acid ; but 

 I found, on adding it to the settled infusion, that a copious 

 yellow precipitate was presently formed. 



This would, therefore, seem to warrant the conclusion, that 

 whilst a certain principle in the Peruvian bark (probably cin- 

 chonia) which combines with the acid, remains soluble in 

 water ; a part, in the caramacata infusion, which combines with 

 the acid, is insoluble in watery menstrua, and is precipitated. — 

 This may be the active principle of the latter bark. 



The cinchona infusion remained covered, and exhibited 

 little or no change on the 20th. This suggested the idea that 

 the acid kept it longer, and led to some experiments, which 

 were begun on the 23d ; and the results were, that the infusion 

 of the bark alone became foetid in a few days, the cinchonic 

 odour was lost, and it had no taste of the bark. Others, with 

 addition of vitriolic acid, retained their taste and odour, even 

 for months afterwards. In all of them, however, a fungus or 

 mouldy flake formed on the surface. — Those with the addition 

 of bueyari, ginger, liquorice, together with the acid, remained 

 least changed. That with lemon-peel was more acescent, 

 owing probably to the mucilage of the peel. The liquorice 

 covers the acerbity of the infusion and retards decompo- 

 sition. 



As to the respective values of the two kinds of bark in com- 

 mon use, the pale and yellow, — although the pale is said to 



* I neglected to notice, at the time, what kind of bark the sample was 

 from with which I made these trials, as when I commenced it was not 

 with intention of experiment : I can only say, it possessed all the sensible 

 qualities of the very best bark: (probably the pale). It was from Apo- 

 thecaries' Hall, Glasgow, and was sent out for Plantation Reliance, 

 Essequibo, in 1826 or 1827. 



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