226 EXPERIMENTS AND OBSERVATIONS ON CINCHONA, 



fufion and tindlure of cinchona, containing all the foluble 

 principles of that fubftance, whereas Seguin's obfervations 

 are (aid to be derived from the examination of the ifolated fe- 

 brifuge principle, of which he gives the following characters : 

 " It precipitates the folation of tan, but not the folutions of 

 liifiifionand gelatine and fiilphate of iron." On the contrary my experi- 

 tinftur- of c'n- ments teach me, that the entire infufion and tinflure of cin- 

 pitatefo^rdGns cho"''^> precipitate the folution of tan, and alfo the folution of 

 of tan, gela- gelatine ilightly, and the folution of fulphate of iron co- 

 phate of iron". P'Oii%- But as the two laft precipitates may be reafonably 

 afcribed to the adion of other principles contained in my in- 

 fufion and tindure of cinchona, 1 thai 1 not intifl: upon them, 

 but proceed to tlievv that, although cinchona adually does pre- 

 cipitate the folution of tan, yet it does not contain gelatine. 



Experiment I. 

 Experiments is (fl) An onnce of infufion of galls was faturated, by adding 

 proof of this. |y j|- j,^ different portions, an ounce and a half of infufion of 



Infufion of galis . ' . i ■ i . ■ i /- 



precipitated by cmchona. The mixture was white and turbid, with a loofe 

 infufion of cin- light precipitate. 



(b) On filtration the fluid pafTed almoft colourlefs, and per- 

 feftly tranfparent, 



(c) The precipitate when dried, weighed. five grains. It 

 bad a yellow colour, and an opaque earthy appearance, was 

 extremely friable, and did not adhere to the filtering paper. 



■Gave a further {d) The filtred fluid gave no further precipitate with folu- 

 ^'SX^ "^''^ *'°" °^ cinchona, but with half an ounce of folution of ge- 

 latine, containing fix grains of gelatine in each ounce, it pro- 

 duced a copious precipitate, and was faturated. 



(e) The precipitate, when feparated by filtration, and dried 

 alfo, weighed five grains, but was hard and brittle, adhered 

 flrongly to the paper, had a yellow colour, and exadly re- 

 fembled a refin in appearance. 



Experiment II. 

 Infufion of - (a) An ounce of the fame infufion of galls was faturated by 



galls precipi- ounce and a half of the fame folution of gelatine. Imme- 



tated by gela- . .... . , n r 



tine. diately a very copious, whitifh, tenacious, and adhelive pre- 



cipitate was formed. 



(/;) On filtration the fluid paflfed very (lowly, and even after 

 repeated filtration, f^ill retained a flight degree of opaline 

 bluiflinefs, 



(c) The 



