66 Royal Society : — 



of deciding readilv whether cinchonidine is present ia specimens of 

 cinchoninc or cinchonicine ; all evidence of quinine or its allies 

 having been decided in the negative by the results of the previous 

 tests, as proposed by Brandes, Vogel, Pelletier, Leers, or the author. 



The cinchonidine of Wittstein has also, by the same method, been 

 proved by the author to be totally different from the cinchonidine of 

 Pasteur. 



Acetic acid and chloroform may also be employedfor discriminating 

 between cinchonine and cinchonidine. 



The chemical characters of all these iodo-salts furnish no means of 

 discrimination, for as a class they all agree in being more or less 

 soluble in spirit, giving a deep sherry-brown solution, from which 

 water precipitates them in an amorphous form, as dark brown, cin- 

 namon-brown or purplish-brown coloured precipitates ; they are 

 only very slightly soluble in dilute spirit, and scarcely at all in 

 water, ether, turpentine, or chloroform : acetic, dilute sulphuric, or 

 hydrochloric acid have but little action upon them, whilst concen- 

 trated hydrochloric or sulphuric acid decomposes them. Nitric 

 acid rapidly acts upon them, even in the cold, with violent evolution 

 of nitrous acid and production of heat, iodine being oftentimes libe- 

 rated in the crystalline form. 



Alkalies also decompose them. 



Sulphuretted hydrogen, soluble sulphides, sulphurous acid and 

 sulphites, together with chlorine-water, instantly decolour their 

 alcoholic solution, with the production of hydriodic acid. 



In dilute alcoholic solutions, starch gives immediate evidence of 

 iodine, and nitrate of silver gives a yellowish-white precipitate of iodide 

 of silver, and some organic basic compound which can only be re- 

 moved by the action of concentrated boiling nitric acid ; this reac- 

 tion, although commencing at the ordinary temperature, with violent 

 disengagement of nitrous acid vapours, must be perfected by boiling. 



Baryta salts exhibit the existence of sulphuric acid, which in all 

 instances is an essential constituent in their formation. 



The quinidine and cinchonine salts dissolve with more difficulty, in 

 consequence of their greater thickness and less extent of surface. 



Since the author had the honour of communicating his discovery 

 of the optical salt of cinchonidine to the Royal Society, he has 

 ascertained that its primary form is, like that of the quinine salt, 

 that of a right rhombic prism, and usually very thin, but having 

 for its acute angles 43°, and 137° for its obtuse, with the rectangular 

 axes M^.-p^ ; Ty -y^^j ; P^'j^ni xpj — the quantity for P" being variable 

 and very minute. In a former communication to the Royal Society, 

 the quinine salt was shown to have a primary rhombus, having 65° 

 for the acute, and 1 1 1")" for the obtuse angles, with the three rectan- 

 gular axes, thus related : — Mxtt^ ; T^.-ij^^ ; PVuttot- 



In both salts the optical characters are usually examined through 

 the shortest axis, V" : in some recent observations on the quinine 

 salt, the author has discovered that it transmits a blood-red beam of 

 ulane-polarizcd light through the axes M° and T", and this is also t\ 

 Ream polarized in a plone parallel to that of the axes M" and T*. 



