38 Observations and Experiments on Peruvian Bark. 



is not very strong, but when bark is well cured it is always 

 perceptible, and the stronger it is, provided it be pleasant, 

 the better may the bark be considered. In order to give 

 bark the form of quill, the bark gatherers not unfrequently 

 call in the aid of artificial heat, by which its virtues are de- 

 teriorated, the fraud is detected by the colour being much 

 darker, and upon splitting the bark, by the mside exhibiting 

 stripes of a whitish sickly hue. In the form of powder, cin- 

 chona is always found more or less adulterated. This must 

 he recollected as applying to the English market. During a 

 late official inspection of the shops of apothecaries and drug- 

 gists, the censors repeatedly met with powdered cinchona 

 having a hard metallic taste, quite foreign to that which 

 characterizes good bark.* The best test of the goodness of 

 bark, is afforded by the quantity of cinchona or quina that 

 may be extracted from it ; and the manufacturer should al- 

 ways institute such a trial before he purchases any quantity, 

 taking a certain number of pieces indiscriminately from the 

 bulk. 



Before concluding, it may not be out of season to remark, 

 that the sulphate of quinine, as it is generally termed, is not a 

 perfectly neutral salt, but in the state of a sub-sulphate, and is 

 only partly soluble in water. Its exhibition in water is render- 

 ed much more eligible by the addition of a drop of sulphuric 

 acid to each grain of the salt, which makes a perfectly trans- 

 parent solution, and which, I think, from its obvious advan- 

 tages, should entirely supercede the common formula ; with 

 sugar and gum arabic, a few grains of citric or tartaric acid 

 will have the same effect in dissolving the quinine as the sul- 

 phuric acid, and has been preferred by some. 



Dr. Paris,! on the exhibition of quinine, states that he 

 lately saw a prescription in which the salt is directed to be 

 rubbed with a few grains of cream of tartar, and then to be 

 dissolved in mint water. This, he continues, is obviously in- 

 judicious, since tartaric acid decomposes the sulphate, and 

 occasions an insoluble tartrate which is precipitated. 



* Mr. Thompson has suggested the probability of this circumstance having 

 arisen from the admixture of a species of bark, lately introduced into Europe 

 from Martinique, resembling the cinchona flnribunda, and which by an anal- 

 ysis of M. Cadet was found to contain iron. — London Diep. Edit. 3, p. 247. 



I Pharmacologia, Edit. 6, vol. ii, p. 163. 



