336 MICROCHEMISTRY OF PLANT PRODUCTS 



brown color. A solution of potassium bichromate or potassium 

 iodide in 50 per cent, sulphuric acid produces, with berberin, 

 an intense purplish-red color. One part of nitric acid mixed 

 with 100 parts of water added to sections containing berberin 

 will produce clustered acicular crystals of berberin nitrate 

 within the berberin-bearing cells. 



Betulin, Cj^Hj808 + H20. — This glucoside occurs in the 

 form of fine granules in the thinner walled cork cells of birch 

 bark. It is accompanied by the enzyme betulase, which splits 

 it into glucose and methylsalicinic ester. In order that it may 

 be studied to good advantage under the microscope, the air 

 should be pumped from sections immersed in water, and then 

 the sections should be examined in water under the microscope. 

 Betulin is insoluble in water, but is soluble in alcohol. It is 

 strongly antiseptic, and protects birch bark against the attacks 

 of lower organisms. 



Betuloretic Acid, CggHggOj. — This is secreted by the 

 glandular hairs on the leaves of Betula alba. It is obtained 

 from the thick, pale yellow secretion by successive solution in 

 boiling alcohol, ether, and an aqueous solution of sodium 

 carbonate. It is colored a beautiful red by concentrated sul- 

 phuric acid. 



Brucine, C23H2eN204 + 4H20. — The alkaloid brucine oc- 

 curs along with strychnine in the seeds of various species of 

 Strychnos. Ammonium vanadate in sulphuric acid gives with 

 brucine a yellowish-red color. When sections containing brucine 

 are treated with a mixture of nitric and hydrochloric acids, 

 the cell-contents are colored a reddish-orange, which merges 

 into yellow. 



Cafifeine, CgHjoN^Oj + HjO.— The narcotic alkaloid in 

 many foods and drugs. It occurs in plants of various families; 

 for instance, in Thea, Coffea, Theobroma, Cola, Ilex, Sterculea, 

 Neea. When sections containing caffeine (theine, methyl- 

 theobromine, trimethyl-xanthin) are treated with a drop of 

 concentrated hydrochloric acid, and then after a minute with 

 a drop of a 3 per cent, gold chloride solution, somewhat slender. 



