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yellow.

Saturated (boiled).

Angle o. Depth 3.7 mm.

Weak band in blue and blue-green.
Intense, green fluorescence. Absorp-
tion complete from 0.20/1 to 0.25/1
and then decreases to transparency
at 0.29/1. Weak absorption ex-
tends from about 0.46/1 to 0.505/1.

143. Guinea Carmine B. (A.)
Similar to fig. 20, pi. 5.

Brown powder. In solution red, pink.

Saturated.

Angle 2 17'. Depth 0.26 to 1.51 mm.

Absorption in green. No lines trans-
mitted between 0.20/1 and 0.273/1.
(Non-zero depth of liquid.) Weak
absorption from 0.273/1 to 0.33/1.
Transparent from 0.33/1 to 0.493/1.
A aazy-edged band extends from
0.493/1 to 0.548/1 with its maximum
at 0.521/1. Transparent from 0.548/1
to 0.63/4. The spectrogram for solu-
tion No. 143 does not slant at the



143. Guinea Carmine B Continued.

red limit, whereas that for solution
No. 127 does.

144. Orcein.

Suggested by figs. 20 and 21 of pis.
5 and 6, respectively.

Black powder with reddish tinge. In
solution deep red, light red.

Saturated (heated and filtered).

Angle 31.2'. Depth o to 0.29 mm.

Weak, narrow band in the yellow. The
ultra-violet absorption is similar to
that of solution No. 127. The ab-
sorption in the visible spectrum is
somewhat like that of solution No.
46. However, the band in the yel-
low is very much weaker and nar-
rower for solution No. 144 than for
the corresponding band of solution
No. 46. Strong absorption from
0.20/1 to 0.27/1 was followed by a
gradual decrease to transparency
near 0.33/1. Transparent from 0.33/1
to about 0.515/1. A narrow, hazy-
edged absorption band, with its
maximum at 0.525/1, extended from
0.515/1 to 0.542/1 approximately. The
very marked slant of the end of the
spectrogram showed the presence of
comparatively intense, general ab-
sorption in the orange.

145. Soluble Prussian Blue.

Deep-blue, glistening powder. In so-
lution deep blue, blue.

1.76 g. per liter.

Angle 21.3'. Depth o to 0.18 mm.

Strong absorption in the yellow,
orange, and red. Almost opaque
from 0.20/1 to 0.28/1. Absorption
decreases very gradually from 0.28/1
to 0.38/1. The visible region of ab-
sorption begins at 0.505/1 and con-
tinues to 0.63/1 and beyond.

146. Thiogene Brown S. (M.)
Similar to fig. n, pi. 3.
Bluish-black lumps. In solution dull

brown, brown.

Saturated.

Angle 27.3'. Depth o to 0.25 mm.

General weakening of all the visible
spectrum except the blue and red.
The solution smells strongly of
hydrogen sulphide. (The odor is
not so marked for the dry dye.)
Similar absorption to that of solu-
tion No. 47. Absorption decreases
very gradually from 0.20/1 to about



4 6



ATLAS OF ABSORPTION SPECTRA.



146. Thiogene Brown S Continued.

0.41/4. On both sides of 0.445/4 the
absorption is at a minimum. A
very shadowy band absorbs from
0.49/1 to 0.545/1. Its maximum is
near 0.523/4. The end of the nega-
tive slants a good deal more than
that of solution No. 47, and thus
points to the absorption in the yel-
low and orange.

147. Thiogene Orange R. (M.)
Similar to fig. 12, pi. 3.

Brown powder. In solution reddish
brown, yellow.

5-83 g- per liter (filtered).

Angle 50.7'. Depth o to 0.46 mm.

Weak absorption in the violet. The
solution has an unpleasant odor. Its
absorption is similar to that of solu-
tion No. 30. Absorption is complete
from 0.20/4 to 0.25/1 and then de-
creases with a long, gentle curve to
transparency about 0.445/4. Trans-
parent from 0.445/1 to 0.63/1.

MISCELLANEOUS ABSORBING MEDIA.

148. Acetone, Ethyl Alcohol, Methyl Alco-

hol, and Water.

Fig. 87, pi. 22.

The depth of the cell was 1.41 cm. for
each of the liquids studied. Especial
care was taken to have the three
organic solvents as nearly anhy-
drous and as pure as possible.

The photographic strip nearest to the
comparison spectrum gives the ab-
sorption of the column of acetone.
The next strip in order corresponds
to ethyl alcohol. The third strip per-
tains to methyl alcohol and the
strip nearest to the numbered scale
is the photographic record for dis-
tilled water.

Acetone absorbed all radiations be-
tween 0.20/4 and 3282.4 A. U. and
the continuous background as far as
3302.7 A. U.

The most refrangible spark line trans-
mitted by the ethyl alcohol had the
wave-length 2265.1 A. U. This
liquid transmitted all the strong
ultra-violet lines, but it absorbed the
continuous background from 0.20/4
to about 0.275/4.

The methyl alcohol transmitted very
faintly the strong cadmium line at
2313.0, but no other radiation of



148. Acetone, Ethyl Alcohol, etc. Cont'd.

wave-length less than 2502.1. The
continuous background in the ultra-
violet, on the contrary, was trans-
mitted somewhat more freely by the
methyl than by the ethyl alcohol.

The distilled water was perfectly trans-
parent to all the radiations in the re-
gion photgraphed.

These results show that even ethyl
alcohol is not without sufficient ab-
sorption in the remote ultra-violet to
make it necessary to take this factor
into account when columns two or
more cm. long are used.

149. Aesculine.
Fig. 73, pi. 19.

White powder. In solution colorless.

Saturated.

Angle 39.0'. Depth o to 0.36 mm.

No visible absorption. Intense, blue
fluorescence. Absorption decreases
from 0.20/1 to semi-transparency
about 0.26/4. Partial transparency
from 0.26/4 to 0.273/4. The band
with which the fluorescence is prob-
ably associated extends from 0.273/4
to 0.363/4 with the maximum near
0.32/4. Complete transparency from
this band to 0.63/4 and beyond.

150. Aluminium Chloride, Calcium Bromide,

and Calcium Chloride.

Fig. 88, pi. 22.

The depth of the cell was 1.41 cm. for
each of the solutions studied. The
photographic strip nearest to the
comparison spectrum gives the ab-
sorption of the calcium bromide so-
lution. The next strip in order corre-
sponds to the aluminium chloride.
The third strip from the compari-
son spectrum pertains to the calcium
salt. The remaining strip shows the
lack of absorption possessed by dis-
tilled water.

The concentrations of the aluminium
chloride, calcium bromide, and cal-
cium chloride solutions were, re-
spectively, 2.75, _ 4.24, and 4.51
normal. The unit used here is the
gram-molecular normal ; that is, i
liter of solution of unit concen-
tration would contain I gram
molecule of the anhydrous salt.

The aluminium chloride solution trans-
mitted faintly all of the strongest



MISCELLANEOUS ABSORBING MEDIA.



47



150. Aluminium Chloride, etc. Continued.

lines in the remote ultra-violet, but
it absorbed the continuous back-
ground from o.2Ofi to about 0.288/1*.

The calcium bromide solution trans-
mitted nothing between o.2O/x and
2748.7. The intensity of this strong
cadmium line was greatly diminished.
The continuous background began to
be perceptible photographically at
about o. 313/4.

The calcium chloride solution trans-
mitted faintly all of the strongest
lines in the remote ultra-violet, but
it absorbed the continuous back-
ground from o.2O/i to about 0.280^..

Consequently there is no very marked
difference between the absorptions
exerted by the two chlorides. The
bromide, on the other hand, pos-
sesses much stronger absorption in
the ultra-violet region of the spec-
trum.

151. Barium Permanganate.

The absorption is identical with that
of potassium permanganate solu-
tions, having the same concentration
in the MnO 4 ions. See No. 179.

152. Calcium Bromide.
See No. 150.

153. Calcium Chloride.
See No. 150.

154. Carborundum and Dia- <^> a

mond.* Q b

Fig. 89, pi. 22. o c

Eight crystalline plates of & '
carborundum and three
of diamond were fastened f
to a strip of black paper
in such a manner as to
bridge across different
parts of a long, slit-like
opening in the paper.
The carborundum plates
varied in color from
visible transparency to
deep blue. The carbons
were colorless. The ac-
companying sketch shows
approximately the size,
shape, relative positions,
and distribution of blue of F- 7-
the plates, d, e, and f denote the
diamonds. The paper strip was slid
over the slit of the spectrograph, par-
allel to the length of this opening,
and successive exposures were taken.




1 54. Carborundum and Diamond. Cont'd.
The absorption produced by plates
a, b, c, d, and e was first photo-
graphed, then the absorption of /
and g, next that of h and i, and
lastly, that of / and k. The spark
and glower exposures were 75 sec.
and 60 sec., respectively.

Plate a was uniformly colored a blue
of moderate intensity. Its absorp-
tion is shown by the photographic
strip, the outer boundaries of which
are numbered I and 2. In cases
where the crystals were not in con-
tact the light passed through be-
tween them and produced narrow
comparison spectra ; for example,
the strip between Nos. 2 and 3.

Plate b was almost colorless with a
frosted surface. Thickness 0.036
mm. Its absorption spectrum is the
strip between 3 and 4.

Plate c had about the same color as
plate a. Thickness 0.173 mm. Its
absorption spectrum is the strip be-
tween 5 and 6.

Plate d was a smooth, colorless car-
bon. Thickness 0.191 mm. Its
spectrum is between 6 and 7. c and
d were practically in contact. This
pair of plates shows how much more
transparent to ultra-violet light pure
carbon is than a colorless plate of
carborundum of comparable thick-
ness. Judging by the negative the
former transmits no light of wave-
length shorter than 2748.7 A. U.,
whereas the latter absorbs everything
shorter than 0.390/1.

Plate e had such an irregular surface
that the light transmitted by it did
not fall upon the sensitized film.
Thickness about 0.191 mm. The
blank between 10 and n is due to
translation of the photographic film
between the first and second settings.

Plate f was a diamond with irregulari-
ties running parallel to the slit.
Thickness 0.533 mm - Spectrum be-
tween n and 12.

Plate g was a deeper blue than any of
the above-mentioned crystals in the
pentagon nearer plate f. The wide
border, extending around four sides
of the blue area, was practically
colorless. Thickness 0.602 mm.



Kindly loaned by Mr. I<. E. Jewel),



4 8



ATLAS OF ABSORPTION SPECTRA.



1 54. Carborundum and Diamond Cont'd.

Spectrum between 13 and 14. / and
g contrast diamond, colorless car-
borundum, and blue carborundum
with one another. The blank from
14 to 15 marks the second setting
of the film.

Plate h had a delicate, uniform, blue
tint. Thickness 0.064 mm - Spec-
trum between 16 and 17.

Plate i was a deeper blue than any of
the preceding crystals. Thickness
0.345 mm. Spectrum between 18
and 19. The blank from 19 to 20
corresponds to the third setting of
the photographic film.

The center of plate / was as deep in
color as the middle of i and it was
also the thickest plate studied. Thick-
ness 0.693 mm - Spectrum between
20 and 21.

Plate k was of a delicate blue color of
a slightly deeper hue than plates b
and c, except in the corner nearer /.
In the latter place it had about the
same tint as plate h. Thickness
0.097 mm - Spectrum between 22
and 23.

155. Chromium Chloride.

Fig- 79. Pi- 20-

In solution very dark green, green.

Saturated.

Angle 50.7'. Depth, from nearly o to
0.46 mm.

Strong absorption in the violet, blue,
orange, and red.

Absorption was complete from 0.20/1
to 0.303/1.. The boundary of the
ultra-violet band curved around
from 0.303/4 to 0.328/1 as the thick-
ness of absorbing layer increased
from its least to its greatest value.
Semi-transparency from 0.328/1 to
0.380/1. A wide, round band, with
its maximum near 0.438/1, absorbed
from 0.380/1 to 0.498/1. This is fol-
lowed by fairly complete transmis-
sion from 0.498/1 to 0.555/1. The
orange and red region of absorp-
tion commenced at about 0.555/1.

156. Cobalt Chloride.
Fig. 78, pi. 20.

In solution red, rose-pink.
35 1 -9 S- f anhydrous salt per liter
(2.71 normal).



156. Cobalt Chloride Continued.
Angle 58.5'. Depth 0.53 to 1.07 mm.
One absorption band in the blue-green

and another in the deep red.* Ab-
sorption was complete from 0.20/1 to
about 0.248/1. The solution was
quite transparent from 0.25/1 to
about 0.495/1. An absorption band,
with its maximum near 0.520/1, ex-
tended from 0.497/1 to 0.542/1. Trans-
parent from the boundary of this
band as far as the deep red.

157. Cobalt Chloride and Aluminium

Chloride.
Fig. 95, pi. 24.

The plane-parallel cell was kept at the
constant depth of 1.41 cm.

The successive solutions were made up
in the following manner: First, a
chosen volume of the mother-solu-
tion of cobalt chloride was run from
a burette or pipette into a measur-
ing flask. Next, a certain amount
of the mother-solution of aluminium
chloride was run into the same flask
and mixed with the solution of the
cobalt salt. Finally, distilled water
was added to the mixture until the
resulting solution filled up the meas-
uring flask to its calibration mark.
Of course, all the usual precautions
necessary to avoid errors due to
changes in volume on mixing and to
lack of homogeneity were taken.
Each solution of the series was made
up to the same volume and con-
tained the same amount of cobalt
chloride. On the other hand, the
mass of the dehydrating agent pres-
ent changed from one solution to
the next.

The photographic strips nearest to the
numbered scale and to the compari-
son spectrum correspond, respec-
tively, to the solutions which con-
tained the least and greatest amounts
of the aluminium salt. The inter-
vening strips succeed one another in
the order of increasing percentages
of aluminium chloride. The con-
stant concentration of the cobalt
chloride in the solutions was 0.271
normal. The concentrations of the
aluminium chloride in the several



* For exhaustive details tee " Hydrates in Aqueous Solution," etc. Harry C. Jones, Publication No. 60 of the
Carnegie Institution of Washington.



MISCELLANEOUS ABSORBING MEDIA.



49



157. Cobalt Chloride, etc. Continued.

solutions of the series were o.ooo,
i.irS, 1.394, 1.676, 1.781, 1.887,
2.096, and 2.459 normal.

The solution which contained no dehy-
drating agent only absorbed the con-
tinuous background from 0.20/1 to
0.23 1 jit. The band in the blue-green
extended from 0.503/1 to about
0.530/1.

The solution of concentration 2.096,
in the aluminium chloride, absorbed
the continuous background from
0.20/1 to 0.288/1. The band in the
blue-green extended from 0.485/1 to

0-555/*-

The absorption in the yellow and
orange is brought out clearly by the
photographic strip adjacent to the
comparison spectrum. The changes
which the bands in the orange and
red undergo when the amount of
dehydrating agent in the solutions is
increased are pronounced and inter-
esting, but they are too complicated
to admit of discussion in this place.*
Similar changes are brought about
by other dehydrating agents, such
as calcium chloride, for example.

Figure 95 illustrates the fact that the
absorption bands of a colored salt,
so-called, can be widened by the addi-
tion of suitable colorless salts as well
as by simple increase in concen-
tration.

158. Cobalt Chloride in Acetone.

Fig. 90, pi. 23, and fig. 94, pi. 24.

Fig. 90 shows the changes in the posi-
tions of the centers of the regions
of absorption and transmission of
cobalt chloride produced by varying
the solvent. The depth of the cell
was 2.40 cm. Counting from the
comparison spectrum towards the
opposite side of the spectrogram, the
four photographic strips correspond
to solutions of anhydrous cobalt
chloride in water, in absolute methyl
alcohol, in absolute ethyl alcohol, and
in anhydrous acetone, respectively.

The aqueous solution was rosy red.
The methyl solution was purple.
The color of the ethyl solution was
blue with a slight reddish tinge. The
solution in acetone was blue with a



158. Cobalt Chloride in Acetone Cont'd.

slight greenish tinge. The concen-
trations of the solutions, in the order
named, were, respectively, 0.325,
0.099, 0.097, an d o.oio normal.
The aqueous solution absorbed prac-
tically all radiations from 0.20/1 to
0.275/1. The blue-green band ab-
sorbed the region between 0.45/1 and



The solution having methyl alcohol for
solvent absorbed all of the ultra-
violet from 0.20/1 to near 0.39/1. It
then transmitted from 0.39/1 to
0.495/1. The next absorption band
extended from 0.495/1 to 0.56/1. The
faintness of the associated photo-
graphic strip shows the presence of
appreciable absorption in the yellow.

Both the ultra-violet absorption and
the adjoining region of transmis-
sion were very nearly the same for
the solution in ethyl alcohol as for
that in methyl alcohol. On the con-
trary, the third strip gives no indi-
cation of return to transparency in
the yellow of the band which ab-
sorbed all of the green.

The acetone solution transmitted the
region between about 0.38/4 and
0.56/1, but absorbed all the other
radiations which could affect the
Seed film.

The phenomena in the visible spectrum
were brought out very clearly by
photographing with a Cramer
"Trichromatic" plate. The depth of
the cell was decreased to 2.00 cm.

The aqueous solution transmitted
from beyond the shorter wave-
length end of the plate to 0.46/1 and
again from 0.543/1 to beyond 0.625/1
at the other end of the plate.

The solution in methyl alcohol trans-
mitted from 0.387/1 to 0.495/1 and
again from 0.548/1 to beyond 0.625/1.
The intensity of the transmitted
light, in the yellow and orange, how-
ever, was not as great for the
methyl as for the aqueous solution.

The solution in ethyl alcohol only trans-
mitted from 0.385/1 to 0.497/1.

The solution in acetone only trans-
mitted from 0.373/1 to 0.560/1.



*For exhaustive details see "Hydrates in Aqueous Solution," etc. Harry C. Jones, Publication No. 60 of the
Caruegie Institution of Washington.



ATLAS OF ABSORPTION SPECTRA.



158. Cobalt Chloride in Acetone Cont'd.

It is thus seen that the photographic
center of the band of absorption in
the green was displaced by about
200 Angstrom units as the solvent
was changed from water to methyl
alcohol. A still greater displacement
was produced by changing from the
one alcohol to the other, the concen-
trations of the two solutions being
very nearly equal.

The empirical data given above serve
to illustrate* the general fact that
the position and character of a
given region of absorption or of
transmission of a chosen colored
salt can be varied, in general, over
wide ranges by suitable changes in
the solvent used.

Fig. 94 shows the way in which the
limits of absorption change when
water is added to solutions of anhy-
drous cobalt chloride dissolved in
absolute acetone. The depth of the
cell was 2 cm. The solutions were
made up in the following manner:
A certain arbitrary volume of water
was poured into a measuring flask
and then the flask was filled up to
its calibration mark by running into!
it from a burette the requisite amount
of a mother-solution composed of
anhydrous cobalt chloride and abso-
lute acetone. When water is gradu-
ally added to such a mother-solution
the resulting liquid changes by de-
grees from deep blue through light
blue and then through an almost
colorless condition to faint pink.

The percentages by volume of the
water in the solutions under consid-
eration were, o, 2, 4, 6, 8, 10, and 12.
The concentration of the mother-
solution was 0.015 normal.

The photographic strip nearest to the
comparison spectrum corresponds to
the solution which was anhydrous.
The next strip pertains to the solu-
tion which contained 2 per cent of
water, and so on, across the entire
spectrogram. The mother-solution
absorbed completely all radiations
between 0.20/4 and 0.333/11. The con-
tinuous background was very much
weakened as far as about 0.361/4.
The solution transmitted freely



158. Cobalt Chloride in Acetone Cont'd.

from this wave-length to near
0.552/4. A strong absorption band
commenced at 0.552/4 and extended
into the red.

The photographic strip pertaining to
the solution which contained the
smallest measured amount of water
transmitted from 0.333/1 to about
0.566/4. The change in absorption
due to the addition of water to the
anhydrous mother-solution is, there-
fore, more noticeable in the ultra-
violet than in the yellow. The photo-
graphic boundary of the ultra-violet
absorption band changed but little,
as the percentage of water present
in the solutions increased from 2 to
12, and this is due to the intense
ultra-violet absorption of the pure
acetone. (See No. 148.) On the
other hand, acetone possesses no ab-
sorption band in the visible spectrum,
and hence the limits of transmission
in the green and yellow, as shown
by the several strips of the spec-
trogram, represent correctly the
changes in absorption consequent
upon the addition of successive in-
crements of water.

159. Cobalt Chloride in Ethyl Alcohol.
See 'No. 158.

160. Cobalt Chloride in Methyl Alcohol.
See No. 158.

161. Cobalt Glass.
Fig. 85, pi. 21.

A plane-parallel sheet of ordinary blue
cobalt-glass was ground to the form
of a wedge and then polished. A
prism of colorless glass was at-
tached at the sides to the cobalt prism
with its refracting edge parallel to
that of the colored glass. The two
wedges were in contact over their
hypothenuse planes, and hence the
outer plane surfaces were nearly
parallel. The object in using the
colorless glass wedge was, obviously,
to correct for the dispersion of the
cobalt-glass prism. The lack of
agreement between the contiguous
edges of the two photographic strips
shows that the angle of the color-
less prism ought to have been at
least twice as large as that of the
blue prism. The angle of the cobalt-



*See also No. 165.



MISCELLANEOUS ABSORBING MEDIA.



161. Cobalt Glass Continued.

glass wedge was approximately 9.
The compound system absorbed all
the ultra-violet from 0.20/4 to 0.325/4.
The boundary of the ultra-violet
band does not curve or slant very
much with reference to the long axis
of the spectrogram because of the
absorption of the colorless glass in
this region of the spectrum. The
cobalt-glass transmits from about
0.327/1 to 0.497/4. Beginning at
0.497/1 a region of absorption ex-
tends into the red. The most re-
frangible band in this region has its
maximum near 0.52/1. The mini-
mum of absorption between the band
just mentioned and the less refran-
gible, neighboring band is at wave-
length 0.560/1. The band in the
orange extended into the red beyond
the field of view of the spectrograph.
These results were tested by using
a red-sensitive photographic plate.

162. Cobalt Sulphate.
Similar to fig. 78, pi. 20.

Reddish crystals. In solution red, sal-
mon pink.

Saturated.

Angle about 6. Depth o to about 3.2
mm.

Rather weak absorption in the blue-
green. All of the strongest ultra-
violet lines were transmitted. The
continuous background was absorbed
from 0.20/4 to about 0.255/1. The
band in the blue-green extended
from 0.505/1 to 0.525/1 with its center
near 0.515/4.

163. Copper Chloride.
Fig. 77, pi. 20.

Dark-green crystals. In solution dark
green, yellowish green.

534-7 S- f anhydrous salt per liter
(3.98 normal).

Angle 19.5'. Depth nearly o to 0.18 mm.

Intense absorption in the red. The
solution was remarkable for its
strong absorption of the ultra-violet
radiations. Absorption was complete
from 0.20/4 to 0.32/4 at the thinnest
part of the wedge. The end of this
band curved around from 0.32/4 to
0.40/4. Transmission was complete
from about 0.40/4 to the orange.



164. Copper Chloride and Calcium Chlo-
ride.
Fig. 92, pi. 23.

The plane-parallel cell was kept at the
constant depth of 1.41 cm. The
several solutions were made up as
explained under No. 157, which see.
The photographic strips nearest to
the numbered scale and to the com-
parison spectrum correspond, re-
spectively, to the solutions which
contained the least and greatest
amounts of the calcium salt. The
intervening strips succeed one an-
other in the order of increasing per-
centages of calcium chloride. The
constant concentration of the cop-
per chloride in the solutions was
0.398 normal. The concentrations
of the calcium chloride in the sev-
eral solutions of the series were
o.ooo, 0.271, 0.541, 0.812, 1.082,
1.353, 1-624, 1-894, 2.165, 2.435,
2.706, 2.977, 3-247, 3-5I8, 3.788, and
4.041 normal. The addition of cal-
cium chloride to an aqueous solution
of copper chloride changes the color
of the latter from clear blue, through


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