38 MICRO-CHEMICAL REAGENTS. 



tissues of higher plants during observations on the 

 division of the nucleus. 1 



MERCURIC NITRATE (Millon's reagent). 2 



This is made by dissolving mercury in its weight 

 of concentrated nitric acid, and diluting with an 

 equal volume of distilled water. It should be 

 freshly prepared when required for use. 



It causes the cell-wall to swell, and so renders 

 its striation more evident, but its most important 

 use is for the detection of protein compounds. 

 These, after lying in it for some time, and espe- 

 cially after slight warming, assume a very red color. 

 The surface membrane (Hautschicht) of proto- 

 plasm is slightly colored if at all. It should, how- 

 ever,, be added that the reagent is not very sensitive, 

 and the reaction is not always obtained (Nageli). 



CHLORIDE OF GOLD. 



A one-half per cent, solution has recently been 

 used in America for coloring the tissues of fungi. 

 It requires from one to six hours to produce the 



1 Treub: Quelques recherches sur le role du noyau dans la division des 

 cellules vegetales, 1878, p. 9. Naturk. Verh. d. koningl. Akad., Vol. XIX., 

 Amsterdam. 



2 Dippel : Das Mikroskop, I., p. 281 ; II., p. 18. Nageli : Das Mikroskop, 

 1877, pp. 475, 527. Weiss : Allgem. Bot., I., pp. 77, 144. Millon: Ann. 

 de Chim. et de Phys., 3 Ser., Tome 29, p. 507. Radlkofer : Ueber krystal. 

 proteinart. Kb'rper, Leipzig, 1859. 



