forty centuries of ink-第30部分

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always　know　of　the　circumstances　which　surround

the　placing　of　original　ink　on　paper　and　that　be　cannot

manufacture　the　TIME　which　has　already　elapsed；

it　is　not　strange　that　attempted　fraud　can　often　be

made　evident　and　complete　demonstrations　given　of

the　methods　employed。



With　the　passage　of　time；　the　particles　in　some

inks　which　are　held　together　on　the　paper　by　gummy

vehicles；　commence　to　disintegrate　and　change　from

intense　black　to　the　brown　color　of　iron　rust；　the

〃added〃　color　which　of　itself　is　fugitive　in　character；

soon　departs；　the　vegetable　astringent　separating

from　the　iron　salt　decays　gradually　and　disappears

and　finally　terminates　in　a　mere　stain　or　dust　mark

which　can　be　blown　off　the　paper。　Sometimes；　the

written　surface　of　such　paper　can　be　treated　by　carefully

moistening　it　with　a　decoction　of　nut…galls　or　its

equivalent　in　the　presence　of　a　weak　acid；　then　if　any

iron　be　present；　a　measurable　degree　of　restoration　of

color　will　ensue　and　remain　for　a　short　period。



Again；　the　discoloration　of　an　iron　ink　may　be　due　to

the　character　of　the　paper；　if　of　the　cheaper　grades

and　the　bleaching　compounds　employed　in　their

manufacture　are　not　thoroughly　washed　out；　then　the

ink　not　only　begins　to　absorb　oxygen　from　the

atmosphere　but　the　chlorine　in　the　paper　attacks　it

and　the　process　of　destruction　is　thereby　hastened。



The　introduction　of　acid　into　ink　has　two　purposes；

one　to　secure　more　limpidity；　and　the　other　to　cause

it　to　penetrate　the　paper　and　in　this　way　bind

together　the　constituent　particles　of　both　ink　and

paper。　Most　of　the　chemical　writing　fluids　of　this

decade　carry　a　superabundance　of　acid　in　their

composition；　which　in　time　will　burn　through　the　paper

and　ultimately　destroy　it。



All　tanno…gallate　of　iron　inks　require　some　vehicle

to　hold　their　particles　in　a　state　of　suspension；　otherwise

there　would　be　precipitation　and　such　an　ink

could　not　be　used。　To　meet　this　requirement　a

variety　of　gums　are　employed　by　manufacturers；

gum　acacia　being　the　principal　one。　Its　purpose　is

threefoldas　before　stated；　to　hold　the　ink　particles

in　suspensionto　prevent　the　ink　from　flowing　too

rapidly；　and　after　drying　WITHOUT　blotting；　to　act　as

an　envelope　to　encase　the　now　fixed　ink　and　prevent

or　interfere　with　its　absorption　of　an　excess　of　oxygen。

The　longer　these　latter　conditions　obtain　the　longer

will　the　ink　retain　its　pristineness；　its　durability　and

permanence。　The　〃time　proved〃　ink…written　specimens

of　five　hundred　years　or　more　ago　which　continue

to　retain　their　original　intense　black　color　and

〃glossy〃　appearance；　do　not；　however；　yield　any　evidence

of　the　use　of　vegetable　gums　in　their　composition。

Where　such　instances　have　been　noticed　the　gloss　is

invariably　missing。　But；　where　ANY　gloss　is　present；

it　was　and　is　because　of　the　employment　of　isinglass

（fish…glue）　as　the　vehicle　to　hold　the　ancient　ink

particles。



Hence　the　variations　of　color　seen　in　ancient　paper

writings；　as　already　stated；　were　due　not　only　to　possible

imperfect　admixtures　of　the　component　parts　of

the　inks；　but　to　the　use　of　vegetable　gums　in　their

preparation。　In　the　course　of　time　these　have　been

absorbed　by　moisture　which　hastened　disintegration；

causing　a　gradual　disappearance　of　their　original　blackness

and　gloss　and　finally　a　return　to　the　rusty　color

of　oxidized　iron。



It　therefore　follows；　my　observations　and　deductions

being　correct；　the　older　a　writing　made　with

tanno…gallate　of　iron　ink；　where　isinglass　is　the　binder；

and　which　has　not　been　〃blotted；〃　the　harder　and

more　impervious　and　irresponsive　it　becomes　to　the

action　of　the　natural　elements　or　of　chemical　reagents。



The　truths　demonstrated　in　this　proposition　cannot

be　denied。　They　fortify　as　certain　that　a　properly

proportioned　mixture　in　water　of　an　infusion　of　nut…

galls　or　gallo…tannic　acid　and　sulphate　of　iron；　with

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；　Hof