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isinglass as the vehicle to bold the particles in a state
of suspension； if written with on good paper and allowed
to dry without blotting； in a short time becomes
encased or enveloped in such vehicle； which is thereby
rendered substantially insoluble and absolutely
prevents any extensive oxidation。 Also； as a further
consequent result； there is chemically created an
unchangeable and continuing black color more permanent
and durable than the substance on which it appears。
With a sample of standard commercial chemical
writing fluid； write on 〃linen〃 paper without blotting
it； in thirty hours； if exposed to the air and
from three to five days if kept from it； the writing
should have assumed a color bordering on black； it
becomes black at the end of a month under any conditions；
and so continues for a period of about five
or six years； when if examined under a lens of the
magnification of ten diameters； there will be a noticeable
discoloration of the sides or pen tracks which
slowly spreads during a continuing period of from ten
to fifteen years； until the entire pen marks are of a
rusty brown tint。 A species of disintegration and
decay is now progressing and when approximately
forty years of age； has destroyed all ink qualities。
If； however； 〃chemical writing fluid〃 is first treated
by exposure to the fumes of an ammoniacal gas； a
〃browning〃 of the ink occurs； not only of the pen
tracks but of the entire ink mark。 If examined now
with a lens； the ink is found to be thin enough to permit
the fibre of the paper to be seen through it； thus indicating
artificial age。 Furthermore； if a 20 per cent
strength of hydrochloric acid be applied； the 〃added〃
color （usually a blue one） is restored to ITS original
hue； alike experiment on 〃time〃 aged ink gives
only the yellow brown tint of pure gall and iron
combinations； the 〃added〃 color having departed caused
by its fugitive characteristics。 Again； if a solution of
chlorinate of lime or soda be applied； the ink mark
is instantly bleached； where in the case of honest old
ink marks； it takes considerable time to even approximate
a like result。
To confirm the chemical tests which may be employed
in the determination of the artificial aging of
ink marks； photographs made by permitting light to
transmit through the paper and to interfere with its
rays by filtering them through a 〃color〃 screen containing
orange and some green； will indicate the presence
of a fugitive substance in the ink； usually the
〃added〃 color employed in its manufacture。
The process of bleaching or 〃removal〃 of ink marks
from paper is frequently employed in the attempted
eradication of words or figures and the substitution
of others on monetary instruments； commonly called
〃raising。〃 Its purpose is usually a criminal one and
some observations as to the modus operandi and its
chemistry are not out of place here。
Ink marks made with a compound consisting of the
combination of iron and an infusion of galls or its
equivalent （a tanno…gallate of iron ink）； as treated
with certain chemicals； change from a compound with
color to a chemical compound； with no color。 Nothing
has in fact been absolutely removed or eradicated；
but it is a mere change of form； a sort of re…arrangement
of the particles； the ingredients which formed
the original color being still present； but in such a
condition that they are invisible to the eye。 A restoration
of the invisible ink marks so that they can
be observed； becomes possible by the use of chemical
reagents and is the reverse of the one of erasure or
bleaching； and changes the constituents again into a
compound which has color from the one which had
none。 It does； not； however； reproduce the exact composition
originally existing。 Such a reagent simply
goes to the basis of the material as first used； takes
up what was left and reforms the particles sufficiently
to make them abundantly recognizable。 An apt
illustration of these chemical changes of color is found
in what is known as the phenolphtalein test solution；
which is colored deep purplish…red by alkali hydrates
or carbonates； and then by the addition of an acid
rendered colorless； to be again reddened by an over…
plus of the alkali and so on ad infinitum。
A popular material for the purpose of making
chemical erasures is chlorinated lime or soda； which
becomes more active by first touching the ink mark
to be removed with a one half strength solution of
acetic acid； this hastens the liberation of chlorine
gas； THE active agent which causes the 〃bleaching〃
to take place。 Hydrogen peroxide； also a bleaching
compound； is less rapid in its action than chlorinate
of soda； the same may be said of combinations of
oxalic and sulphurous acids。
The most effective re…agent for the restoration of a
chemically 〃bleached〃 iron ink mark is the sulphide
or sulphuret of ammonia （it has several names）。 This
penetrating chemical blackens metals or their salts；
whether visible or not； if brought together。 It must
not be used by direct contact； the best and safest
plan being to place a quantity in a small saucer； to be
set on the floor of a closed box； to fasten to the box
lid the specimen to be operated on； in this way the
restoration is due to the fumes of the chemical and a
possible danger of destruction of the specimen much
lessened； especially if the marks are very light or delicate
ones。 The restoration of color under particular
conditions may also be obtained by treatment with
tannic acid； potassium ferro…cyanide （acidulated） or a
weak solution of an infusion of galls。
CHAPTER XVIII。
INK CHEMISTRY。
SOME OBSERVATIONS AS TO CHEMICAL EXAMINATION OF
INK MARKS BY ALLENERASING OF INKS BY CHEMICAL
MEANSAPPROVED CHEMICAL TESTS IN THE
ASCERTAINMENT OF INK CONSTITUENTS。
A COMPILATION of the methods of Robertson；
W。 Thompson （Lord Kelvin）； Irvine； Wislar； Hoffman
and others； relative to the chemical examination of ink
marks； is to be found in 〃Allen's Commercial Organic
Analysis。〃 Their experiments； however； date back
many years ago； a few of them before the time of the
use of the 〃anilines〃 for added color。 The so…called
〃alizarin〃 ink referred to has now become obsolete。
The following is the citation in part：
〃In chemico…legal cases it is sometimes of
importance to ascertain the nature of the ink used；
to compare it with specimens of writing of known
history； and to ascertain the relative ages of the
writings。 A minute inspection should first be
made with a magnifying power of about 10 diameters；
and any peculiarities of color； lustre； shade；
etc。； duly noted； and where lines cross each other
which lie uppermost。 The examination is often
facilitated by moistening the paper with benzine
or petroleum spirit； whereby it is rendered semi…
transparent。 The use of alcohol or water is inadmissible。
〃Valuable information