OTHER ORGANIC COMPOUNDS. 45 



ASPARAGIN. 



Borodin ' has recommended a tepid concentrated 

 aqueous solution for the detection of asparagin, 

 which has been precipitated in the tissue by alcohol 

 (p. 27), on the principle that a crystallized sub- 

 stance is insoluble in a saturated solution of the 

 same substance. 



Asparagin is prepared by evaporating the well- 

 boiled and filtered sap of young seedlings of legu- 

 minosae (especially lupines) which have germinated 

 in the dark, or by the evaporation of the dialyzed 

 aqueous decoction of althaea root ; when it sepa- 

 rates as crystals. 



DIPHENYLAMIN. 



This officinal substance has of late been used as 

 a reagent for nitrates and nitrites. 2 The sections 

 to be tested are allowed to dry on the slide and 

 afterwards moistened with a solution of .01-. i gm. 

 of diphenylamin in 10 cc. pure sulphuric acid. 

 Even very small quantities of compounds contain- 

 ing nitric acid are indicated by the appearance of 

 a dark blue color in the cells ; the reaction is very 

 distinct. 



1 Borodin : Bot. Zeitung, 1878, p. 804, et seq. Detmer : Physiol. u. 

 Keimiing d. Samen, 1880, p. 171, et seq. 



2 Molisch : Ueber den Mikrochemischen Nachweis von Nitraten und 

 Nitriten etc. Ber. d. deutschen hot. Ges., 1883, I., p. 150. 



