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forty centuries of ink-第36章

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ink。



〃2d。 The application of a thin layer of gum; of

starch; or farina; of gelatine; or fish…glue; with a

view of sizing certain parts of the paper; or of

causing certain bodies to adhere to it momentarily;

is detected by an action similar to that which

shows paper to have lately been wetted by the contact

of liquids。



〃3d。 The heterogeneousness of the pulp of the

papers; and the kind of size with which they are

impregnated; lead to differences in the results

which are observed with the same chemical reagents。

We shall now examine each of these propositions;

and describe the means which we have

employed in endeavoring to solve questions of so

high a degree of interest。



〃1st。 The homogeneousness of sized paper not

partially altered by the contact of liquids (water;

alcohol; salt…water; vinegar; saliva; tears; urine;

acid salts; and alkaline salts) is demonstrated by

the uniform coloration which this surface takes on

being exposed; if not wholly; at least in various

parts; to the action of the vapor of iodine disengaged

at the ordinary temperature from a flask

containing a portion of the metalloid。 When the

surface of paper not stained by any of the above

mentioned liquids is exposed to the action of this

vapor for three or four minutes in a room the temperature

of which is about 60 degrees F。; a uniform yellowish;

or light…brownish yellow; coloration is noticed

on the whole extent exposed to the vapor of

iodine; in the contrary case; the surface which has

been moistened; and afterwards dried in the open

air; is perfectly distinguished by a different and

well circumscribed tint。 On the papers into which

paste starch and resin have been introduced; the

stains present such delicate reactions that we may

sometimes distinguish by their color the portion of

paper which has been moistened with alcohol from

that which has been moistened with water。 The

stain produced by alcohol takes a bistre…yellow

tint; that formed by water is colored of a more or

less deep violet blue; the desiccation having been

effected at the ordinary temperature。 For the

stains occasioned on these same papers by other

aqueous liquids; the tint; apart from its intensity;

resembles that of the stains of pure water。 The

feeble or dilute acids act like water on the surface

of the same paper containing starch in its paste;

but the concentrated mineral acids; by altering

more or less the substances which enter into the

composition of the latter; give test to the stains

which present differences。 We are always able

to recognize by the action of the vapor of iodine

the parts of the paper which have been put in

contact with chemical agents; the energy of which

has been arrested by washing in cold water。 We

are able; on several ancient deeds; written on

stamped paper; and a few words of which had

been removed by us with chemical agents; to

recognize the places where their action was exerted;

to see and to measure the extent which they occupied

on the surface of the paper。



〃The testing of a paper with the vapor of

iodine will present this double advantage over the

methods hitherto practiced for detecting falsifications

in writings; that it points out at once the

place in the paper in which any alteration may be

suspected; and that; on the other hand; it enables

us to act afterwards with the reagents proper for

causing the reappearance of the traces of ink; when

that is possible。 If the means which we now propose

cannot always make the former writing

appear; they demonstrate the places where the

alterations must have been made; when; however;

the want of uniformity presented by the surface

of the paper is not explained by any circumstance。

This proof becomes; therefore; a weapon which

the guilty person cannot avoid。 But might not

the presence of a stain; or several stains; developed

by the vapor of iodine; in different parts of a public

or private deed; give rise to a suspicion; where

these stains have; perhaps; been occasioned by the

spilling of some liquid on the surface of the paper?

and would it not be rash and unjust to raise an

accusation from such a fact? There would indeed

be great temerity in drawing such a conclusion

from a fortuitous circumstance; but the inference

which may be drawn from the place occupied by

these stains on the surface of the paper; from the

more or less significant words found in those places;

would not permit an accusation to be so lightly

brought; where simple reasoning would be sufficient

to destroy its basis。 Besides; the subsequent reactions

which would be made would certainly never

revive words formerly written and effaced; whilst

the latter effects may be often produced; more or

less visibly; on those parts of the paper on which

falsification has been practiced; figures or words

being substituted for other figures or words。



〃2d。 The applications made to the surface of

a sheet of paper; with a view of covering it again

at certain parts with a fine layer of gum; gelatine;

starch or flour paste; or in other places to cause

other sheets of paper to adhere; may be recognized

not only by the reflection of light falling upon the

paper inclined at a certain degree of obliquity; and

by the transmission of light through the paper;

but also by the varying action which the vapor of

iodine exerts on the surface which is not homogeneous。

Papers containing starch and resin are

more powerfully acted upon by this vapor than

papers of a less complex composition。 Both in

the parts covered with starch; or paste flour; are

colored in a few minutes of a violet blue; but

with starched papers alone a more intense coloration

is manifest on the places covered again with a

thin layer of gum arabic; size or gelatine。 By

looking; then; on the surface of the paper; held

somewhat obliquely to incidental light; we distinguish

clearly; by their different aspects; the parts

on which these various substances have been

applied。 The vapor of iodine; in condensing at

the ordinary temperature on the surface of the

papers to which any kind of size has been applied

in various places; produces differences which are

most commonly well recognized by the greater or

less transparence of the paste of the paper。



3d。 The heterogeneousness of the pulp of the

various papers of commerce; and the nature of

the size with which they are penetrated; cause

differences; either in the coloration which the surface

of these papers takes when exposed to the

vapor of iodine; or in the tint which is manifested

in the portions of the size deposited in certain

portions of that surface; thus; papers with starched

pulp generally turn brown; or blue; according to

the amount of water that remains in their interstices;

other papers turn yellow only under the

influence of the vapor of iodine; and the parts

which have received superficially a layer of another

agglutinative body resist this action for a certain

time; and are distinguished from the parts of the

paper which are not covered with it。〃



My own investigations confirm to a great extent

the value of these experiments and the accuracy of

the deductions; in so far as they relate to 〃linen〃

paper; but they do not always obtain when made in

connection with paper of inferior grades。



It is also true that dry paper is affected differently

under the influence of the vapor of iodine; as would

be paper which had been moistened and then dried;

but the part which had been moist assumes the color

of blue…violet; while unaltered paper assumes a yellow…

brown color。 Even when the paper thus treated is

moistened all over with water; there will be a difference;

for those parts which had been before moistened;

will appear a dark violet…blue; while the other parts

will show a plain blue coloration。



In cases where pencil writing has been removed

with a soft rubber or fresh bread; the parts thus

erased will assume; when subjected to iodine fumes; a

brown color trending towards violet and much darker

than the undisturbed portions of the paper。 Lines

impressed upon paper with a 〃stylus;〃 a glass or

ordinary dry pen; can be made visible by the fumes of

iodine; the lines showing with a stronger coloration

than the surrounding paper。







CHAPTER XX。




FUGITIVE INK。



SOME OBSERVATIONS ABOUT 〃ADDED〃 COLOR TO INK

INVENTION OF COAL TAR COLORSCHRONOLOGICAL HISTORY

OF THE 〃ANILINES〃 EMPLOYED AS INKOTHER

SUBSTANCES USED FOR THE SAME PURPOSE。



THE term 〃added color;〃 as applied to ink; is the

popular phraseology for a multitude of materials

which have been more or less utilized for a period of

centuries; in adulterating and coloring ink。 In olden

times they were introduced into ink with an honest

belief that it would also improve and ensure its lasting

qualities; but latterly more often to cheapen the

cost of 
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