a newhj-discovered Salt of Quini?ie. 165 



quinine in a given solution. It is to be regretted that the atomic 

 weight has not yet been determined, but hitherto time has not 

 permitted the necessary experiments to be undertaken. 



This substance presents itself under a variety of crystalline 

 forms ; a slight change in the manner of producing them will 

 occasion an alteration in their shape. (See fig. 2.) 



When formed from a solution of the disulphates of quinine 

 and cinchonine in diluted sulphuric acid, they present the form of 

 parallelopipeds, exceedingly slender and elongated; the terminal 

 planes are rectangular, the thickness being scarcely appreciable, 

 even less than T J^dth part of an inch, the breadth and length 

 being variable. 



The transition from this form to the square plate is very easy, 

 and frequently observed. 



By truncating the angles of the square plate we derive the 

 octagonal plate; very common. 



Under other circumstances, the aciculaj change the form of 

 their terminal planes and become acutely pointed. 



By shortening the length and increasing the breadth we ob- 

 tain the half hexagon. 



By joining two of these, base to base, we obtain the hexagonal 

 plate. Very frequently found in crystals deposited from the 

 acetic acid solution. 



The rhomboidal plate is a very common form. 



When a quantity of the disulphates is dissolved in acetic acid, 

 a very few drops of a spirituous solution of iodine employed (say 

 four or five), and the mixture left some hours in perfect repose to 

 cool and crystallize, very large broad plates are produced, appa- 

 rently formed of many aciculfe cohering by their elongated edges. 

 These plates, by very careful manipulation indeed, may be trans- 

 ferred to a thin plate of microscopic glass and dried ; when set up 

 in Canada balsam and properly mounted, this becomes available 

 as a polarizer ; and in this way a crystal has been mounted by 

 the author, and adapted to his microscope in place of a tourma- 

 line. Frequently these crystals assume a form derived from the 

 cuboid plate, several of which joined edge to edge produce a 

 compound plate, the angles being at the same time more or less 

 truncated. 



Occasionally the constituent rhombic or square plates cohere 

 by their flat surfaces instead of by their edges. They are all 

 arranged in the same optical plane; and are not merely superim- 

 posed by accident in this peculiar position, all the crystals formed 

 in the solution having the same extraordinary shape. 



Under other circumstances we obtain this substance in the 

 form of most beautiful compound rosettes, the component crystal 

 being either the minute hexagon or a form derived from it ; or 



