46 MICRO-CHEMICAL REAGENTS. 



BRUCIN 



Has been introduced into micro-chemistry for the 

 same purpose as diphenylamin, but it does not 

 serve so well for the detection of small quantities 

 of nitrates and nitrites. Molisch ' recommends a 

 solution of .2 gm. brucin in 10 cc. pure sulphuric 

 acid. A dry section of a tissue which contains 

 N 2 O 5 assumes a bright red or reddish-yellow tint 

 when placed in a drop of the solution. 



INDOL. 



This substance has been employed quite recently 

 by Niggl as a reagent for lignin, or lignified mem- 

 branes. 2 The discovery of this reaction is due to 

 Professor Baeyer, of Munich. 3 Several crystals of 

 indol are dissolved in a sufficient quantity of warm 

 distilled water. The sections to be tested are 

 placed in a drop of the reagent for several minutes, 

 after which they are washed in dilute sulphuric 

 acid (i pt. : 4 pts. water). Lignified cell-walls 

 assume a very intense red color. 



PHLOROGLUCIN. 



One of the prettiest and best reactions of micro- 

 chemistry has recently been discovered by Wiesner ; 



1 Molisch : Ber. deutsch. hot. Ges., 1883, 1., p. 150. 



2 Niggl: Flora, 1881, No. 35, p. 545. 



8 Ann. d. Chem. u. Pharm., Bd. CXL. 



