October. lOin. 



KNOWLEDGE. 



389 



to poison him by lea\'ing a bottle of stout containing 

 prussic acid at his lodgings : but. instead of Parker 

 getting the stout, it was drunk by his landlord and 

 landlady, both of whom died. As a great deal 

 depended upon whether Parker were speaking the 

 truth or not. the ink was obtained 

 from the public house in question, 

 and was compared with the 



the best l<nowti 

 the age of an ink 



wTitmg upon the will. 



As this ink happened to contain 

 a particularly bright blue pigment 

 as its provisional colouring matter, 

 there was no difficult\- in pnning 

 its identit\- with the ink in the 

 disputed signature on the will. 

 In fact three different inks were 

 present on this w ill, the bod\- of 

 the document lieing written in 

 one kind of ink, and the signatures 

 of each of the witnesses in a 

 different kind. Brinkley, cross- 

 examined upon this point, stated 

 that Mrs. Blume had kept three 

 different sorts of ink. and that he 

 death, given two of them to a little girl. 



^ in.*}, ^*^l''^. 



1 SQS 





results olitained with some of 

 commercial writing inks. 



The question of determining 

 in writing is much more difficult than that of 

 deciding whether two writings are in the same or 

 in a different kind of ink. 



It is, as a rule, possible io dis- 

 tinguish colorimetricalh' between 

 freshly-written and old writing 

 up to about the sixth da\-, after 

 which the iron tannate has become 

 sufficiently oxidised tt) prevent 

 f .^ ■ further differentiation until after 



i^' the lapse of two or three years 



> • or more, when the provisional 



^ * pigment will have faded or have 



become fixed by the iron tannate. 

 In most cases, the provisional 

 1908. pigments emploved, offer greater 



resistance to the action of chemi- 

 cal reagents, but are infinitely less 

 stable than iron tannate when 



Figure 2. 



Showiiii,' the action of oxalic acid on ink;; 

 written in 1S9,S and 190,S. 



After a trial lasting four 



had, after her 

 uilt\- 



^f^^i.c.<.aUi 



davs he was foimd 

 of murder, and sentenced to death. 



For the differentiation of writing by chemical 

 methods a w ide choice of reagents is available, but 

 the following will usualh' be found sufficient : — 

 (1) Hydrochloric acid (5 per cent, solution) : (2) 

 oxalic acid (5 per cent, solution) : (3) stannous 

 chloride (10 per cent, solution); 

 (4) nascent h\-drogen (.50 per cent. 

 HCl. with zinc) ; (5) bromine (satur- 

 ated aqueous solution) ; (6) bleaching 

 powder (saturated solution) ; (7) titan- 

 ous chloride ; and (8) potassium ferro- 

 cvanide (5 per cent, solution, con- 

 taining 1 per cent, of HCl.). 



Of these reagents the two first act 

 mainly upon the iron tannate and 

 leave the provisional colouring matter. 

 The third and fourth bleach the iron 

 tannate and reduce the provisional 

 pigment, changing its colour. The 

 fifth and sixth reagents may act upon 

 both pigments and cause more or less 

 bleaching. The titanous chloride acts 

 as a powerful reducing agent on both pigments, and 

 the acidified ferro-cyanide solution acts mainly upon 

 the iron liberated from the iron tannate. 



The reagents should be applied with a brush, and 

 the writing examined imder the tnicroscope by 

 reflected and transmitted light, firstl\- after five 

 minutes", and then after twelve hours' exposure to 

 the air. The colorations appearing on the wrong 

 side of the paper are also characteristic in some 

 cases. In the tests with titanous chloride, blotting 

 paper should be applied to the writing after the 

 lapse of five minutes. 



The method ma\' be illustrated b\- the following 



JET S^^uM^^ 



(^ 



1898, 



1908. 



Figure 3. 



Showins; the action of acetic acid 



l50'/ii) on inks written in 1898 



and 1908. 



exposed to the action of light and 

 air, and eloquent testimon\- to this difference is given 

 b\' a com[)arison of certain manuscripts of the se\'enth 

 antl eighth centuries with t\'pe-written documents in 

 aniline ink. which ha\-e been put aside for a few 

 }-ears. 



Thus it happens that when writing done with 



blue-black ink is kejit, the blue pigment will 



gradualK' fade out. leaving the black [ligment, and 



when this stage is reached the ink in old writing is 



readih- distinguished from ink that 



has recenth' been [)ut on the paper. 



Prior to this, howe\'er, the blue 

 provisional colouring matter appears 

 to become en\'eloped in particles of 

 the oxidised iron tannate, so that it no 

 longer reacts rapidly with reagents. 



Thus, if a writing done within the 

 last \'ear or two be treated with a 

 fift\" per cent, solution of acetic acid 

 there is immediate diffusion of the 

 blue pigment, whereas in a writing a 

 few years older diffusion, if it takes 

 place at all, is very slow and limited 

 in extent (see Figure 3). 



A still more useful reagent is a 

 saturated solution of oxalic acid, which 

 causes the pigment of relatively fresh w riting to give 

 an immediate smudge, but has very little, if an\-, 

 effect on writing six or eight ^■ears old. The differ- 

 ences between the behaviour of old and relativeh' 

 new writing in these tests is seen in Figure 2, 

 in which the older writing of 1898 was scarcely 

 affected, whereas the writing done in 1908 gave the 

 results shown. F>oth writings were in ink of the 

 same kind, and the tests were api:ilied simultaneously. 

 Speaking generally, a writing done with blue- 

 black ink ceases to show such diffusion after about 

 five to six years. When slight diffusion occurs 

 in an older ink it is seen, under the microscope, 



Y 



