The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-10-19


Since an early period in the history of
shemistry, it has been known that the ditfe-
rent alkalies and alkaline earths can be dis
tinguished by the different colorations which
they give to the flame of alcohol. Soda turns
the fame yellow, potassa violet, ithia Grim
son, strontia crimson, lime orange, and baryta
green. Magnesia does not color tho flame.
Many years ago Sir John Herschel and
others experimental upon these lights
with prism. 1t is we'll known that when
q raw of light from the sun or lamp.
after passing through a narrow slit is re-
fracted in direction perpendicular to the
slit, it is not all equally bent but that part
is bent less and part more, so that the light
is dispersed and spread out into a rainbow
colored spectrum. The red light is the least
refracted, and the violet light the most. This
experiment is part of the proof that white
light is composed of red, yellow, green, blue,
indigo, and violet. Now, when Herschel and
other investigators passed the light from the
alcohol flame, colored by alkalies, through a
slit and prism in the same way, they found
that the light was not spread out into a con-
tinuous spectrum from red to violet. The
yellow light derived from soda was not dis
persed at ALL but was all equally refrangible.
Such light is called monochromatic, or
single -colored, because it is not composed of
light of different colors; and in a room illu-
tinguisb colors in the least degree; but
objects which by daylight present the strong
est contrasts in colors, by such light are
precisely alike in that respect. In the case of
the other substances the spectrum is not re-
duced to a single line, nor is it continuous,
but it consists of several narrow lines of diff
ferent colors, separated by black spaces
These we're the first chemical experiments
with the spectroscope they did not mmedi
ately lead to any great discoveries, on account
of the imperfect methods in which furtker
Investigations were conducted.
Accordingly, this instrument never at
tracted much attention until 1860, when the
researches of Kirchhoff and Bunsen were pub
lished From this time may also be dated a
new era in chemistry and astronomy. Kirch-
hoff was young physicist little known be-
fore Bunsen, an eminent chemist. The
fame they made use of was that of the Bun
An gas-burner, which is much better suited
spectroscopio work than that of alcohol,
oth on account of its greater heat and also
kom its freedom from sodium and other i'm
puritieS, which impart color to the flame.
n They proved, in a more rigorous manner than
u former experimenters had done, that
the lines of the spectrum depend
solely on the constituents of the flame,
and not upon its temperature. They also
showed the extreme delicacy of spectroscope-
test in many cases. A platinum wire, which
las Deen Cledueu ny bept dt u WulJe
heat until all that could be volatlized in the
flame has been driven off, if after cooling it
J is passed once through the fingers or any
| CLOTH or even is allowed to remain untouched
for some time, will, when put into the flame,
impart to it the pure yellow light which is
characteristic of sodium. This shows that
there is common salt floating about in the air
of all our houses, and resting upon everything
"A fact quite unsuspected before.
But what drew the most particular atten-
ton to these researches was the discovery by
Bunsen, by means of the spectroscope, of
two new metals. For many years no new
elements had been discovered, but, on the
contrary, great doubt prevailed as to the ex-
istence of those last added to the list-pelo-
plum, norium, and terbium. The establish
mont of the existence of another element
was regarded as labor of many years; yet
in one year rubidium and c9esium, the metals
discovered by Bunsen, were better under
stood in their chemical relations than dozen
others. The reason of this WAS that the spec
troscope afforded a means of securing the
purity of the new substances, which is
always the most difficult part of such
Investigations. Furthermore, the small
proportion (about 1-50000th of one per cent.
in which the new elements occurred in the
mineral water in which they were found, made
their discovery very surprising. Of course
all this created a great sensation in the scien-
oOOh
found in every laboratory. Two other metals
thallium and indium, have since been dis
covered by means of it, with the same cir
cumstances of being found in extremely small
proportions, and of becoming quickly very
we'll understood. But the chemical dis
coveries of the spectroscope were soon to b'
outdone by its performances in the realm o.
astronomy.
The optician Fraunhofer, in 1914, upol
observing the spectrum of the sun with
carefully constructed spectroscope, had OBJ
served that it was crossed everywhere witt
very fine black lines, irregularly distributed
of which he mapped some six hundred l
had been asserted that the most conspicuou
of these lines, called d, corresponded il
position with the yellow line of sodium
Kirchhoff found that this was precisely true
and demonstrated by long mathematics
process that, in general, body cannot b
transparent to the same rays as those wit
which it shines Consequently, the precls
coincidence of the yellow sodium line and tn
line d of the suns spectrum could be az
counted for by supposing that incandescer
sodium vapor existed in the atmosphere @
the sun, which absorbed this yellow part {
the light emitted from the solid sun beneath
In order to obtain the spectra of the heavie
metals they were made the electrodes of
Ruhmkorf coil, whereby heavy electrl
spark was made to pass from one piece {
such metal to another. This spark gives th
spectrum of the metal in the greatest perfet
ton. By comparing the spectra of the metal
thus obtained with the solar spectrum, fou
teen of them have been detected in the soia