KOui . w [Oct, i. 



sence of metals producing green glases in the reducing flame, such as 

 vanadium or chromium, the green being complementary with the red of 

 titanium and thus destroying the latter. That method is purely colorimel 

 ric, as the determination depends on a comparison of color intensity with 

 glass beads containing known quantities of titanium. But the mutual ex 

 tinction of complementary colors led me, already at that date, to seek a 

 way for the utilization of this principle, as expressed in the same paper : 

 "I am now experimenting upon the feasibility of extinguishing the color 

 of titanium by a graduated scale of green, etc' Finding, however, 



some serious practical obstacles, I allowed the subject to rest until the 

 present summer, when perfect leisure favored a more successful pursuit. — 

 I now place before the Society the result in a preliminary form, reserving 

 for a future paper the details and the special determinations, as well as 

 tables, tor a number of the most important minerals and ores. — The new 

 method of analysis I propose to name " chromometry, " tor I measure the 

 quality as well as the quantity of certain colors, both isolated and when 

 combined with other colors not their complementaries, these latter being 

 the determinants. Thus, iron imparts to borax in the oxydizing flame a 

 dark red-brown color while the bead is hot, which passes into pure yellow 

 at the ordinary temperature of the air. Under the same conditions man- 

 ganese produces a purplish-red glass, both together a brown idass in all 

 shades from pure yellow to pure red. according to the relative quantities 

 of the two metals. If this glass be looked at through a certain thickness 

 of a transparent green medium, such as green glass— the red will have dis- 

 appeared and a pure yellow will be seen ; increasing the thickness of green 

 medium ever so little, will cause a greenish yellow color to appear, whilst 

 an equal reduction in the medium will cause a brownish yellow tint. The 

 human eye is much quicker to appreciate a change of shade, than a small 

 change of intensity of color, as those well know, who are accustomed to 

 the polarization of sugar.— In this instance I designate the pure yellow as 

 the point of extinction, while colorlessness or any other simple color may 

 represent extinction in other cases. — Thus it will be understood that the 

 new method analyses the colors, what colorimetry of liquids as heretofore 

 applied does not, it involves another principle and should therefor be called 

 by another name. — Chromometry seems to express the essential" of the 

 method very well "a measuring of color " besides being a purely Greek 

 compound noun, not Latin-Greek, as Colorimetry. The new principle 

 of analysis by complementary colors is applicable to both liquid and solid 

 transparent colored bodies, but I shall confine myself for the present to 



the solid.- eXClUSH ely. 



In regard to their behavior towards borax and microcosmic -alt — the 

 metals are chromatic (imparting characteristic colors to these fluxes) or 

 achromatic (imparting no color, or no characteristic color). — The chromatic 

 -die- comprises: copper, nickel, cobalt, iron, uranium, chromium, van 

 adium, tungsten, titanium, manganese, molybdenum, niobium, ilmenium, 

 neptunium. All of these metalls fall within the capacity of chromometric 



