342 



INDELIBLE "WRITIN& INK, 



The more abundant sediment is owing to a larger quantity 

 of extract and tannate of iron. In inks made by infusion, 

 the oxide of iron, extract, and tannin, increase their oxi- 

 genation ^ery little, till they come to dry on paper. Nitric 

 acid immediately obliterates writing with ink made by in- 

 fusion, but that which has been made by decoction resists 

 its action much longer, on account of the larger quantity of 

 . extract in it. 

 Infusion or de- In proportion as the infusion or decoction of galls grows 

 should be kept ^^^f its surface is covered with mother, which is the muci,. 

 sometime. laginous principle separated. This mother ceases to form 

 in about a year, during which the pellicle produced on the 

 surface should be removed three or four times. The in^ 

 fusion or decoction of galls grows brown as it becomes oxi- 

 genized, takes an amber colour, and emits a pleasing smell ; 

 and, when combined with green sulphate of iron, no longer 

 produces a Prussian blue, but a green black. The amber 

 colour of th,is infusion or decoction is owing to the oxige- 

 nized extract and tannin. The green colour of the ink 

 arises from the mixture of the black of the gallate of iron 

 with the fawn colour of the oxigenized tannin, which in 

 this state can no longer combine with the oxide of iron. If 

 the tannin be separated from the infusion or decoction by 

 means of an alkali, the green or red sulphate of iron forms 

 -with it a very black and purer ink ; and the alkali in the 

 solution facilitates the union of the oxide of iron with the 

 gallic acid, by combining with the sulphuric acid of the sul- 

 phate. The oxigenized extract concurs in rendering the ink 

 blacker, as does the oxide of iron more highly oxided. 

 Infusion of galls is preferable to the decoction, as it dis- 



Infusion pre- 

 ferable. 



Receipt for 

 good ink. 



solves the principle, that is essential to the composition, 

 and very little of those that are foreign to it. Logwood 

 browns the ink, and loads it with its colour; it is better 

 therefore, to use in its stead a small quantity of galls in ad- 

 dition to that directed by Lei^is. The following is the Qomr 

 position of a good ink. 



Infuse in one litre [a wine quart] of rain or river watef 

 1^5 gram. [4 oz. troy] of bruised galls, letting them stand 

 in the sun four hours in summer, or six hours in winter. 

 This infusion may be used immediately after straining; but 



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