FREE BOOKS

Author's List




PREV.   NEXT  
|<   124   125   126   127   128   129   130   131   132   133   134   135   136   137   138   139   140   141   142   143   144   145   146   147   148  
149   150   151   152   153   154   155   156   157   158   159   160   161   >>  
tion with iodine give birth to the blue tint. Consequently the action of the iodine differs according to the extent of the erasure. "When paper is partially erased and wet, as when letters are copied, the same result although not so striking follows upon exposing it to the iodine vapor after letting it dry thoroughly. "Iodine affords in certain cases the means of detecting the nature of the substance used for erasing. Bread crumbs or India rubber turn yellow or brownish yellow tints and these are distinguished by more intense coloration; erasure by means of bread crumbs causing the paper to take a violet shade of great uniformity. These peculiarities are due to the upheaval of the fibers caused by rubbing. In fact this upheaval creates a larger absorbing surface and consequently a larger proportion of iodine can cover the rubbed parts than it would if there had been no friction. "When paper upon which writing has been traced with a glass rod, the tip of which is perfectly round and smooth, is exposed to iodine vapor, the characters appear brown on yellow ground which wetting turns to blue. This change also occurs when the paper written upon has been run through a super-calender. If the paper is not wet the characters can be made to appear or be blotted by the successive action of sulphurous and iodine vapor. "Writing done by means of glass tips instead of pens will show very little, especially when traced between the lines written in ink. The reaction, however, is of such sensitiveness that where characters have been traced on a piece of paper under others they appear very plainly, although physical examination would fail to reveal their existence, but a somewhat lengthy exposure to iodine vapors will suffice to show them. "If the wrong side of the paper is exposed to the iodine vapor the characters are visible; but of course in their inverted position. "If the erasure has been so great as to take off a part of the substance of the paper the reconstruction of the writing, so as to make it legible, may be regarded as impossible. But in this case subjecting the reverse side of the paper to the influence of the iodine will bring out the reverse outlines of the blotted-out characters so plainly that they can be read, especially if the paper is placed before a mirror. In some instances, when pencil writing has been strong enough, its traces can be reproduced in a letter press by wetting a sheet of sized and cal
PREV.   NEXT  
|<   124   125   126   127   128   129   130   131   132   133   134   135   136   137   138   139   140   141   142   143   144   145   146   147   148  
149   150   151   152   153   154   155   156   157   158   159   160   161   >>  



Top keywords:
iodine
 

characters

 

traced

 

yellow

 

writing

 
erasure
 
reverse
 

crumbs

 
upheaval
 

exposed


substance

 

action

 
plainly
 

written

 
larger
 

blotted

 
wetting
 
physical
 

examination

 

successive


sulphurous

 

Writing

 

sensitiveness

 

reaction

 

reveal

 

exposure

 

mirror

 

instances

 

influence

 

outlines


pencil

 
strong
 

letter

 

reproduced

 

traces

 
subjecting
 

visible

 
suffice
 

vapors

 
lengthy

inverted
 

position

 
regarded
 
impossible
 

legible

 

reconstruction

 
existence
 

brownish

 
rubber
 

erasing