forty centuries of ink- 第31部分

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　is　often　obtainable　by

treating　writing　or　other　ink…marks　with　reagents。

Some　inks　are　affected　much　more　rapidly　than

others；　though　the　rate　of　change　depends　greatly

on　the　age　of　the　writing。　Normal　oxalic　acid　（63

grammes　per　litre）；　or　hydrochloric　acid　of

corresponding　strength；　should　be　applied　to　a　part　of

the　ink　marked　with　a　feather　or　camel…hair　brush

（or　the　writing　may　be　traced　over　with　a　quill

pen）；　and　the　action　observed　by　means　of　a　lens；

the　reagent　being　allowed　to　dry　on　the　paper。

Recent　writing　（one　or　two　days　old）　in　gallic　inks

is　changed　by　one　application　of　oxalic　acid　to　a

light　gray；　or　by　hydrochloric　acid　to　yellow。

Older　stains　resist　longer；　in　proportion　to　their

age；　and　a　deeper　color　remains。　Log…wood　ink

marks　are　mostly　reddened　by　oxalic　acid；　and

alizarin　marks　become　bluish；　but　aniline　inks

are　unaffected。　With　hydrochloric　acid；　logwood

ink　marks　turn　reddish　or　reddish…gray；　alizarin

marks　greenish；　and　aniline　ink　marks　reddish　or

brownish…gray。　The　treatment　with　acid　should

be　followed　by　exposure　to　ammonia　vapors；　or

blotting　paper　wet　with　ammonia　may　be　applied。

Thus　treated；　marks　in　logwood　ink　turn　dark

violet　or　violet…black。　The　age　of　ink　marks　very

greatly　affects　the　rate　of　their　fading　when　treated

with　dilute　ammonia；　the　old　marks　being　more

refractory。　The　behavior　of　ink　marks　when

treated　with　solution　of　bleaching　powder　is　often

characteristic；　the　older　writings　resisting　longer；

but　unless　the　reagent　be　extremely　dilute；　writings

of　all　ages　are　removed　almost　simultaneously。

Hydrogen　peroxide　acts　more　slowly　than　bleaching

solution；　but　gives　more　definite　results。　After

bleaching　the　mark　by　either　reagent；　the　iron　of

the　ink　remains　mordanted　on　the　paper；　and　the

mark　may　be　restored　by　treatment　with　a　dilute

solution　of　galls；　tannic　acid；　or　acidulated　ferro…

cyanide。　The　same　reagents　may　be　used　for　restoring

writing　which　has　been　faded　from　age

alone。



〃When　ink　marks　have　been　erased　or　discharged

by　chemical　means；　traces　of　the　treatment

are　often　recognizable。　After　effecting　the　erasure

the　spot　is　often　rubbed　over　with　a　powdered　alum

or　gum　sandarac；　or　coated　with　gelatin　or　size。

The　bleaching　agents　most　likely　to　have　been

used　are　oxalic；　citric；　or　hydrochloric　acid；　bleaching

powder　solution；　or　acid　sulphite　of　sodium。

Moistened　litmus　paper　will　indicate　the　presence

of　a　free　acid；　and　in　some　cases　treatment　with

ammonia　fumes　will　restore　the　color。　The　presence

of　calcium；　chlorides；　or　sulphates　in　the

water　in　which　the　paper　is　soaked　will　afford　some

indication　of　bleaching　powder　or　a　sulphite　having

been　used。　Potassium　ferro…cyanide　will　detect

any　iron　remaining　in　the　paper。　Exposure　to

iodine　vapor　often　affords　evidence　of　chemical

treatment；　and　other　methods　of　examination

readily　suggest　themselves。〃



M。　Piesse；　in　the　Scientific　American；　is　authority

for　a　method　of　removing　ink；　found　on　〃patent〃

check　paper：



〃Alternately　wash　the　paper　with　a　camel's…

hair　brush　dipped　in　a　solution　of　cyanide　of

potassium　and　oxalic　acid；　then　when　the　ink　has

disappeared　wash　the　paper　with　pure　water。〃



Inks　of　the　tanno…gallate　of　iron　family；　whether

containing　〃added〃　color　or　not；　can　be　more　or　less

〃erased〃　by　chlorinate　of　lime　or　soda；　in　the

presence　of　a　weak　acid。　These　chemicals　do　not；

however；　materially　affect　the　prussian　blue　inks；

which　require　solutions　of　hydrate　of　potash　or　soda。

Real　indigo　can　be　removed　by　chloroform；　morphine

or　an　aniline　salt　（indigo　and　aniline　both　owe　their

names　to　the　same　Portuguese　source）；　which　possess

the　rare　property　of　dissolving　pure　indigo。　Such

combination；　if　refractory　in　the　presence　of　permanganate

of　potash　with　sulphuric　acid；　must　be　followed

by　an　application　of　sulphurous　acid。　In　like

manner；　inks　composed　of　by…products　of　coal　tar；　can

be　effectively　treated；　when　irradicable　with　plain

water　or　soap　and　water。



The　erasure　and　removal　of　most　inks　from　paper

can　be　accomplished　by　the　application　of　the　chemicals

heretofore　enumerated。　The　requirements　in

this　direction　of　some　inks；　however；　though　of　rare

occurrence；　are　to　be　met　by　the　employment　of　other

and　particular　reagents。



Many　of　the　tests　specified　in　the　Allen　citation　to

determine　the　character　of　ink　constituents；　if　made

alone　are　practically　valueless；　because　the　same　behavior

occurs　with　different　materials　employed　in　the

admixture　of　ink。　To　avoid　error　in　judgment　the

operator　should　verify　if　possible　by　confirmatory

tests。　Thus；　in　the　one　for　logwood；　sulphurous　acid

will　cause　a　logwood　ink　mark　to　turn　yellow；　mercuric

chloride；　orange；　tartar…emetic；　red；　and　if　the

marks　are　faded　ones；　solutions　of　sulphate　of　iron

or　bichromate　of　potash　will　restore　them　respectively

to　a　violet　or　blue…black　color。



Prussian　blue；　aniline　blue　and　indigo　blue　are　to

be　tested　as　follows：　Solution　of　chloride　of　lime；　no

change　of　color　for　prussian　blue；　decoloration　or

faint　yellow　for　aniline　blue　or　indigo。　To　discriminate

between　the　two　latter；　test　with　solution　of

caustic　soda；　when　decoloration　or　change　of　color

will　indicate　aniline　blue　and　permanence　will　indicate

presence　of　indigo　blue。



In　the　manufacture　of　the　blue…black　inks；　a　variety

of　violets　have　been　and　are　still　employed。　Among

them　are　aniline　violet；　iodine　violet；　madder；　alkanet；

orchil　and　logwood。



（a）　Apply　chloride　of　lime　solution：　1。　No　change

of　color　indicates　alkanet。　2。　Any　change；　one　of

the　other　five。



（b）　Apply　lemon　juice：　1。　The　violet　becomes

brighter　if　it　is　one　of　the　aniline　violets；　to　be

distinguished　from　each　other　by　applying　one　part　of

hydrochloric　acid　to　three　parts　of　water；　when　it　will

become　violet…blue；　changing　to　red　if　it　is　common

aniline…violet；　but　blue　changing　to　a　green　hue　and

upon　adding　plain　water　to　a　lilac　or　pearl　gray　if　it

is　iodine…violet　（Hoffman's）。　It　will　also　turn　from

red　to　yellow　in　lemon　juice。　To　test　for　the　other

three　violets：　（a）　Apply　chloride　of　lime；　to　be　followed

by　a　solution　of　yellow　prussiate　of　potash：

absence　of　a　blue　coloration　leaves　orchil　and　logwood

to　be　considered。　To　distinguish　between　them　apply

solution　of　hydrate　of　lime；　whereby　a　change　to

gray；　followed　by　complete　decoloration　indicates　logwood；

and　a　change　to　violet…blue；　orchil。



The　substances　utilized　with　but　few　exceptions　for

red　ink　are　the　〃eosins；〃　possessing　different　names

like　erythrosine；　as　well　as　different　hues。　Antecedent

to　about　thirty…five　years　ago；　cochineal　（known

as　〃carmine〃）；　madder；　Brazil　wood　and　saffron　formed

the　basis　of　most　of　the　red　inks。



Make　a　soap　solution　adding　a　small　quantity　of

ammonia；　lemon　juice；　muriate　of　tin；　all　in　water：

1。　No　change　upon　application　indicates　madder。

2。　Any　change；　the　presence　of　one　of　the　three　other

reds：　（a）　thus　a　complete　decoloration　with　a　return

of　the　color　indicates　saffron；　（b）　reappearance　of　the

red　color　though　weaker；　aniline…red：　（c）　production

of　a　yellowish　red　or　light　yellow　color；　cochineal　or

Brazil　wood；　to　be　distinguished　from　each　other　by

the　application　of　concentrated　sulphuric　acid；　when

Brazil　wood　will　at　once　give　a　bright　cherry…red；　and

cochineal　a　yellowish　orange。



No　yellow　inks　are　in　commercial　use。　Documents

do；　however；　often　contain　yellow　marks　about　which

information　is　required　as　to　their　origin。　As　a　rule

they　are　iron　rust；　picric　acid；　turmeric；　fustic；　weld；

Persian　berries　or　quercitron。　In　order　to　recognize

the　different　colors；　the　presence　or　absence　of　iron

rust　and　picric　acid　must　first　be　determined。



Apply　a　warm　sample　of　a　slightly　acid　solution　of

yellow　prussiate　of　potash；　iron　rust　will　be　indicated

by　a　blue　coloration。



Apply　a　weak　solution　of　cyanide　of　potassium；　picric

acid　will　yield　a　blood…red　coloration。



If　picric　acid　and　iron　rust　are　both　absent；　apply　a

bit　of　ordinary　wetted　soap：　1。　It　turns　reddish…brown

and　becomes　yellow　again　with　hydrochloric　acid

turmeric；　2。　It　turns　quite　darkfustic；　3。　It　is

unaffectedweld；　Persian　berries　or　quercitron。　To

distinguish　between　these　three；　apply　sulphuric　acid；

the　color　of　weld　will　disappear；　and　of　the　others

remaining　apply　tin…salt　solution；　when　a　change　to

orange　indicates　Persian　berries；　and　no　change　or　a

very　slight　one；　quercitron。



Inks　containing　also　logwood；　fustic；　Brazil　wood；

or　madder；　were　all　of　them　more　or　less　employed

some　years　ago。　Their　color　phenomena；　following

long　periods　of　time；　is　much　the　same。　Tests　as　prescribed

in　the　accompanying　tab