116 Mr. Reit! on Writing-ink, S,-c. 



retains its colour much better than on that which is now in 

 use ; and that the difference which has been observed in this 

 I'espect, so tar as respects writings upon paper, is to be attri- 

 buted to this cause, and not to any difference in the ink. I 

 shall not attempt any explanation of the phaenomenon, but 

 merely state it as a fact *. 



Ink made with either a diminished or an increased quantity 

 of sulphate of iron does not keep its proper colour when writ- 

 ten with upon paper, changing to a brownish black of dimi- 

 nished intensity. When an excess of the sulphate has been 

 used, and the writing has been suffered to remain till the co- 

 lour has been thus impaired, it may be in some measure re- 

 stored by a dilute sulphuric acid. Half a drachm of the acidum 

 sulpJmricwn dilutum of the London Pharmacopoeia, adtled to 

 two ounces of water, brushed over the paper, produces the 

 effect. But if it is used in too large a quantity, or if a stronger 

 acid is used, it injures or destroys the colour altogether. 



With regard to parchment, the skin from which it is made 

 naturally contains a considerable quantity of oil, which pre- 

 vents the ink from fixing upon it. In order to obviate this 

 inconvenience, chalk is used in the manufacture of it, which 

 though it eniibles us readily to write upon it, produces a very 

 injurious effect upon the ink. The sulphuric acid being abs- 

 tracted, an insoluble crust is formed which lies upon the sur- 

 face, but does not penetrate or combine with the substance 

 of the skin. This crust after some time loses much of its 

 colour, adheres so loosely to the parchment that it may be 

 rubbed off with a wet cloth, leaving but little or no mark upon 

 it, — thus affording a ready means of injuring or altering the 

 writing. Nay, the effect is so readily produced, that acciden- 

 tal circumstances, such as rolling and unrolling it, sometimes 

 cause part of the wi-iting to scale oK 



This is a defect of much importance as it appears to me, 

 and one which I have no doubt might be remedied. I have 

 endeavoured to obtain the assistance of those who are practi- 

 cally acquainted with the manufacture of it, to make a series 

 of experiments on the subject, but unsuccessfully. I shall 

 not, however, fail to avail myself of the first opportunity which 

 presents itself to endeavour to discover the means by which 

 the fault may be obviated. 



* The presence of alum is easily- ascertained by tlic test of infusion of 

 roses. Wiieii it is not present, the infusion (made witho'.it acid) causes a 

 pink stain to remain upon the paper: — when it is present, the stain is green. 

 .Sulphuric acid prevents this change when used in a certain quantity. Thus 

 when twice the quantity ordered by the London College, in preparing in- 

 /mum rosa, is added to the sim[)le infusion, the stain is pink ; but if in- 

 fusum roscc itself is used, it assumes a green colour. 



XXII. Oil 



