Dr. Hofmann ow Chloranil. 199 



it changes from a yellow to a bright green colour. The di- 

 stillation need not be long continued, as the kinone is very vo- 

 latile, and comes nearly all over at the first. I have tried this 

 experiment with the genuine barks China ruhra^ China lo.va, 

 and China rcgia, and detected the kinic acid very readily, when 

 less than a quarter of an ounce of each was employed. I have 

 also operated on two ounces of the false bark, China nova Suri- 

 7iamensis, but was unable to detect the least trace of kinic acid. 



It has long been stated in most systems of chemistry, on 

 the authority of Berzelius, that the alburnum of Pinus sylvcs- 

 tris contains a half per cent, of kinate of lime, and that kinic 

 acid exists along with gallic acid in the barks of various other 

 trees. A pound and a half of the inner bark and alburnum 

 of the Pinus sjjlvestris was treated in the way already de- 

 scribed, but I was unable to detect any trace of kinic acid ; 

 though on adding less than two grains of kinate of lime the 

 presence of kinone in the liquid which distilled over was im- 

 mediately perceptible. 



1 may state, in conclusion, that the presence of the vege- 

 table alkaloids quinine or cinchonine in a bark may be readily 

 detected by the following simple experiment. Macerate the 

 bark with dilute sulphuric acid and precipitate with a slight 

 excess of carbonate of soda or potash. Collect the dark-co- 

 loured, very impure precipitate, and distil it with a great 

 excess of caustic soda or potash, cincholin will distil over in 

 oily drops if the bark has contained either of these vegetable 

 alkaloids. Cincholin is easily recognisable by its peculiar 

 taste and smell and its strongly-marked alkaline properties. 

 It is nearly insoluble in water, unless first neutralized by an 

 acid, when it readily dissolves; but it is immediately repre- 

 cipitated in oily drops on the addition of an alkali. It is quite 

 true that the production of cincholin is not a decisive proof 

 that a bark must necessarily contain quinine or cinchonine, 

 as other alkaloids, such for instance as strychnine, also yield 

 it when distilled with potash. The production of cincholin, 

 however, clearly indicates the existence of at least one alkaloid 

 in the bark, the exact nature of which may be subsequently 

 ascertained by the usual methods. 



XXVI. RemarJcs upon Chloranil. 

 By Augustus William Hofmann, Ph.D.^ 



Tj^ IIDMANN t, in his researches upon the action of chlorine 

 -*-^ on indigo, obtained, as the last product of this reaction, a 



* Communicated bv the Chemical Society} having been read December 

 2, 1844. 



+ Journ.fiir Prakt. Ckem.y Bd. xxii. S. 279. [Phil. Mag. S. 3, vol. xix. 

 p. 192.] 



