374 Prof. Eggertz on determining combined Carbon. 
if the regularity be destroyed by rapidly moving the plate m 
irregular directions while breathing upon it, irregular patches 
of color are produced which are the analogues of natural col- 
ored clouds. In fact the rich colors of the sunset are but bro- 
. Consequently, until we pass nearly into a line 
with the sun it is chiefly the blue interference light that reaches 
e eye. 
Philadelphia, March, 1869. 
Ant. XXXVI.—Process for determining the Carbon chet 
cally combined with Iron; by Prof. Eagertz, Director © 
School of Mines, Falun, Sweden.* 
Wuey steel or pig iron containing carbon in chemical com- 
bination is dissolved in nitric acid, a soluble brown coloring 
matter is formed whose coloring power is quite intense, a 
solution assumes a tint which is dark in proportion to the quan- 
tity of the chemically combined carbon. : 
Iron and graphite (or free carbon) do not influence this col- 
oring ; for the solution of nitrate of iron is colorless, or a 
most slightly greenish, unless extremely concentratéd, and 
aphite is insoluble in nitric acid 
_ Thus in dissolving two pieces of different steels of the same 
Weight in nitric acid, taking care to dilute the darker solutiom 
ntil the two liquids present exactly the same color, it is very 
evident that the more highly carburetted steel will furnish ~ 
prog gs of liquid, and that the proportion of the vor 
umes indicate the relative proportion of color in the tw? 
ow the composition and content of carbon of one of the 
steel may be i 
If now 
steels is known, the absolute per centage of carbon in the othet 
immediately deduced. = ° 
_* From the Bulletin of the Chemical Society of Paris: translated for this Jou” 
Wharton, Esq. ~o = : 
RS A og ee eg 
