114 THE MICROSCOPIST. 



some crossed at 60 (Plate III, Fig. 75). Sulphocyanide 

 of potassium produces flat needles, often in groups. Iodine 

 in iodide of potassium gives a reddish-brown amorphous 

 precipitate, crystalline in dilute solutions. When pure, 

 strychnine appears in colorless octahedra, lengthened 

 prisms or granules. To a solution of the alkaloid or its 

 salts in a drop of pure sulphuric acid, which produces no 

 color, add a small crystal of bichromate of potash, and 

 stir slowly with a pointed glass rod. A blue color will 

 appear, passing into purple, violet, and red. The bright 

 yellow crystals of chromate of strychnia, if dried and 

 touched with sulphuric acid, will also show the color test. 

 This is said to be delicate enough to show T0 ^ Tjth of a 

 grain of strychnine. The tetanic convulsions of frogs im- 

 mersed in a solution of strychnine, or after injections of 

 the solution in lungs or stomach, etc , is also a very deli- 

 cate test. 



Veratrin and its salts treated in the dry state with con- 

 centrated sulphuric acid, slowly dissolve to a reddish-yel- 

 low, or pink solution, which becomes crimson-red. The 

 process is accelerated by heat. 



Narcein, touched with the cold acid, becomes brown, 

 brownish-yellow, and greenish-yellow, and if heated, a 

 dark purple-red. 



Solanin turns orange-brown, and later purplish-brown. 



Piperin turns orange-red to brown. 



Salicin gives to the acid a crimson pink, changing to 

 black. 



Papaverin gives a fading purple. 



CRYSTALLINE FORMS OF VARIOUS SALTS. 



Our limits forbid extended description, yet a few forms 

 of frequent recurrence will be useful to the student. For 

 crystals in plants or from animal secretions reference may 

 be made also to succeeding chapters. 



Salts of Lim.e. The carbonate sometimes occurs in ani- 



