112 A HALF-HOUR WITH 



examined after the lapse of a short time, small 

 circular, semi-transparent spots will be found scat- 

 tered over the surface. Further crystallization 

 may be prevented by warming it and mounting in 

 Canada balsam or Dammar. 



The iodo-sulphate of Quinine (Fig. 1, plato 9), 

 also requires special preparation. 



These crystals were first prepared, and their 

 optical properties described by Dr. Herapath, of 

 Bristol. The following are his own directions for 

 making them : 



Mix 3 drachms of pure acetic acid with 1 

 drachm of alcohol ; add to these 6 drops of diluted 

 sulphuric acid (1 to 9). 



One drop of this fluid is to be placed on a glass 

 slide, and the merest atom of quinine added, 

 time given for solution to take place; then, upon 

 the tip of a very fine glass rod, a very minute 

 drop of tincture of iodine is to be added. The 

 first effect is the production of the yellow or 

 cinnamon-brown coloured, composed of iodine and 

 quinine, which shows itself as a small circular 

 spot ; while the alcohol separates in little drops, 

 which, by a sort of repulsive movement, drive the 

 fluid away. After a time the acid liquid again 

 ilows over the spot, and the polarizing crystals of 

 iodo-sulphate of quinine are slowly produced with- 

 out the aid of heat. 



Dr. Herapath also succeeded in producing these 

 crystals in large plates, which could be used in 

 place of tourmalines, and they are called artificial 

 tourmalines or Herapathite. 



Santonine is an alkaloid prepared from the 

 so-called Semen Cynce, or worm seed. It is soluble 

 in alcohol, chloroform, and water. Each solvent 

 alters the character of crystal. With chloroform 

 the crystals assume a lace-like appearance; crystal- 



