24 MICRO-CHEMICAL REAGENTS. 



solution is useful for removing some of the color 

 from too deeply stained sections. A concentrated 

 aqueous solution is used as a test for pectose, 

 which it dissolves after previous treatment of the 

 section with potash. 



CARBOLIC ACID (Phenol). 



This has a very limited application in micro- 

 chemistry. 1 Cell-walls that, after treatment with 

 carbolic acid, assume a greenish-yellow or bluish- 

 green color, when moistened with hydrochloric 

 acid, are considered to be lignified, and phenol 

 thus becomes a reagent for lignin (?). 



Leitgeb 2 has employed a solution of carbolic 

 acid in alcohol as a clearing medium in studying 

 the histogeny of mosses. 



Phenol should be added in small quantity to 

 glycerine-jelly to prevent molding, and when dilute 

 it may be used as a preservative for bacteria 

 (Warming), which remain sharply defined, but be- 

 come clear and homogeneous internally. 



1 Bot. Zeitung, 1877, P- 786- 



2 Nageli: Das Mikroskop, 1877, p. 476. 



