MICROCHEMISTRY. 97 



may be boiled in water to extract the saponin, and then 

 treated in the same way with concentrated sulphuric acid. 



;/. Solanin, C 42 H 7B NO )a . 



162. According to Wothtschall (I), who has tested a great 

 number of reactions as to their applicability, only the three 

 following are suited for the microchemical recognition of 

 solanin. 



1. Mandelin' s Reaction. The reagent for this test should 

 be freshly prepared by dissolving one part of ammonium 

 vanadate in 1000 parts of a mixture of 98 parts of concen- 

 trated sulphuric acid with 36 parts of water. This is added 

 directly to the sections to be studied. In the presence of 

 solanin the following colors appear in order : yellow, orange^ 

 purple-red, brownish-red, carmine, raspberry-red, violet, blue- 

 violet, pale greenish blue ; finally all color disappears. The 

 time in which this scale of color is gone through is chiefly 

 dependent on the concentration of the solutions present, 

 but is always several hours. If any fatty oils are present in 

 the preparation, which would also give color reactions with 

 concentrated sulphuric acid, they may be removed by pre- 

 liminary submersion of the sections in ether, in which 

 solanin is practically insoluble. 



2. Brandt's Reaction. .3 of a gram of sodium selcnate is 

 dissolved in a mixture of 8 ccm. of water and 6 ccm. of 

 concentrated sulphuric acid. After the addition of this 

 reagent to the sections to be studied, the preparation is 

 gently warmed by moving it over a small flame. As soon 

 as the color appears the warming must be stopped. In the 

 presence of solanin there appears first a raspberry-red color, 

 which gradually passes into a currant-red, which soon be- 

 comes paler and more brownish yellow, and finally quite 

 disappears. 



3. Sulphuric Acid. On the addition of concentrated sul- 

 phuric acid, solanin gives at first a bright yellow color, which 

 gradually becomes redder, then takes a violet shade, gradu- 

 ally pales, passes into greenish, and finally quite disappears. 



