110 A. S. Kimball— Physical Properties of Steel. 
very difficult to get rid of. Pulverized, it furnishes a perfectly 
black powder, the smallest particle of which gives before the 
blowpipe a very strong reaction of chromium. Heated very 
intensely, it loses its brilliant color and becomes a dull black. 
The powdered mineral is dissolved completely in nitric acid. 
The solution is intensely green, and furnishes a strong reaction 
of sulphuric acid and oxide of chrome. The other strong acids 
attack it but slightly. 
is solubility in nitric acid readily distinguishes it from 
chrome iron. The quantity of mineral I was enabled to obtain 
pure, or nearly so, was very small, the reaction of the acids on 
the mineral being nearly the same as on troilite. Iam enabled 
to separate them only by varying the strength of the acids, and 
the length of the time they are in contact with the minerals. 
Less than one hundred milligrams were obtained of sufli- 
cient purity to make out its composition, and this amount fur- 
nis me 8648 per 
The following therefore would express its true composition: 
Sulphur 37-62, chrome 62°38. 
This mineral is an interesting one, and is found in a very 
strange place, yet from what is revealed to us by the spectroscope 
with regard to the vapors surrounding the sun, the element 
chrome must be widely diffused in the matter of the universe. 
Art. XIV.—On some of the changes in the Physical Properties 
of Steel, produced by Tempering ; by A. S. KiMBALL, Prof. of 
Physics in the Worcester Institute of Industrial Science. 
pressure of other duties will postpone, for a few months, further 
conductivity and coefficients of expansion. 
odulus of elasticity decreases as the hardness of the steel 
tnereases ; in other words the harder the bar, the greater the de- 
produced by a given weight. 
