lahich are produced upon it by Paper and Parchment. 1 1 5 



thereby forms a greater quantity of ink, it must be diluted with 

 water. To a quart of decoction add three pints and a half 

 of water, and to this add sulphate of iron and gum, of each, 

 nine ounces. The sediment which forms may, after three days, 

 be separated, when it is fit for use. 



Should gallic acid and logwood be used, the followmg pro- 

 portions may be observed : 



Take of galls, one pound. 



logwood, one pound and a half. 



sulphate of iron, eighteen ounces. 



gum, ditto. 



Make a decoction of galls as formerly directed, convert it into 

 gallic acid in the manner described above. When the process 

 fs ended, make a decoction of logwood, by boiling it in five 

 quarts of water till it is reduced to seven pints. Mix this de- 

 coction with the solution of gallic acid, and dissolve the sul- 

 phate of iron and gum. Let them stand for two or three days, 

 and separate the ink from the sediment. 



For the reasons formerly given, it is proper to use the re- 

 cent decoction of logwood, instead of one which has been kept 

 exposed to the air. 



Dr. Lewis's formula for making ink with galls and logwood 

 is so well known that it is unnecessary to give it here. 



Ink, when made, ought to be kept as much as possible ex- 

 cluded from the action of the air, because it gradually suffers 

 a change, in consequence either of the gum or the gallic acid 

 absorbing oxygen, by which its colour is injured ; and inde- 

 pendent of this circumstance, its watery part evaporates and 

 leaves it too thick for use. It ought to be kept in a glass ves- 

 sel, or if in an earthenware one, it ought to be well glazed; for 

 I have often observed that black earthenware inkstands de- 

 stroy its colour,— an effect probably to be attributed to the ac- 

 tion of the argillaceous matter upon the gallic acid. 



Ink suffers decomposition from the action of alkaline sub- 

 stances and their carbonates, the suljihuric acid of the sul- 

 phate being attracted, and the oxide of iron being precipitated 

 in combination with gallic acid, forming a gallate of iron*. 



Before the early part of the eighteenth century, alum was 

 not used in the iiianutacturc of paper, since which time it 

 has been constantly employed. From repeated observations 

 lam convinced that on paper manufactured without it, die mk 



• It has been said that good writinf^-ink may be made by dissolving iron 

 i.i galls; but this is a mistake, h-oii is acted upon by gallic acid; anc as 

 loiii; as there is an excess of acid the compoinid reinanis in solntu.n ; but 

 when -i neutral compound is formed, it is insoluble, and tails down, leaving 

 the w:itcr almost colourless. 



Q 2 rctiiuis 



