42 MICRO-CHEMICAL REAGENTS. 



ORGANIC SALTS. 



ACETATE OF IRON 



Is used in an aqueous solution, as has been de- 

 scribed for the chloride. 



ACETATE OF COPPER (Verdigris) 



Is used as a means of recognizing resins. Masses 

 of tissue are soaked five or six days in an aqueous 

 solution of the salt, after which treatment the 

 resinous masses assume an emerald green color. 1 



SULPHATE OF ANILIN. 



An aqueous solution of this substance, the so- 

 called Wiesner anilin reagent, is used for the detec- 

 tion of lignin, the constituent of wood. 2 The 

 sections are first placed in a dilute solution of the 

 sulphate until they are well saturated with it ; even 

 with no other treatment, lignified membranes often 

 assume a faint yellow color, which, however, is 



1 Franchimont : Origine et constitution chimique des r6sines de ter- 

 penes. Cf. Archives Neerlandaises, 1871, T. VI., p. 427, with PI. 8. 



2 Wiesner: Technische Mikroskopie, 1867^.64, Karsten : Bot. Un- 

 tersuchungen, I., p. 120, note. B urger stein : Sitzungsber. der wiener 

 Akad., 1874, Bd. LXX., Abth. r, p. 338. Hohnel : Ueber Kork, etc. 

 Sitzungsber. der wiener Akad., 1877, Bd. LXXVL, Abth. i, p. 21. - 



