PROFESSOR TRAILL ON THE COMPOSITION OF A NEW WRITING-INK. 427 



Pliny's gluten, however, is very different from mine ; it is common animal 

 glue, but such an ink is removable by water. 



I need scarcely add, that many other prepai'ations of gluten were tried ; but 

 I give a preference to the acetous solution, because it incorporates very freely 

 Anth lamp-black (the cheapest impalpable carbon), and unites all the valuable 

 qualities of the other solutions of this substance. The first step is to prepare a 

 good gluten from wheat-flour, by kneading a mass of the dough below a small 

 stream of water, in order to separate the starch. On the lai'ge scale, this may be 

 done in linen bags or by machinery, but a considerable quantity may be formed 

 in a short time by the hand. The vicinity of a starch-work might probably af- 

 ford this material cheaply. The more perfectly the starch is separated from the 

 gluten the better will be the quality of the ink. When the gluten is kept in 

 Avater for twenty-four or thuiy-six hom'S, it dissolves more readUy in the pyro- 

 ligneous acid than when recently made. The proportions I employ are, — a pound 

 and a half of this gluten to ten pounds of pjToligneous acid, of the specific gra- 

 vity of 1033 or 1034. By the aid of a gentle heat, they form a saponaceous fluid 

 of a greyish- white colour, which wUl keep in this state for long periods. 



The colouring matter should be the best lamp-black, such as is usually sold 

 for 2s. per pound. I find that the colour of the ink, though not its other quali- 

 ties, is improved by the addition of a small quantity of fine indigo. The propor- 

 tions which I employ are from eight to twelve grains of lamp-black and two grains 

 of indigo for every fluid ounce of the vehicle. With the larger proportion, the 

 ink is of a fine deep black ; but it is thought by some persons to flow more easily 

 from the pen, when the smaller proportion of the finest colouring matter is em- 

 ployed, and it seemed also to enter more deeply into the paper. When the lamp- 

 black is of the finest quality, a smaller proportion of this very light and bulky 

 powder wUl suffice than when the lamp-black is coarse, and the ink will be more 

 equal, and flow more smoothly from the pen. It seems scarcely necessaiy to add, 

 that the more completely the ingredients are incorporated, the more perf'ect will 

 be the ink. 



An agi-eeable aroma may be communicated to this ink, by soaking bmised 

 pimento, cloves, or cassia bark, in a portion of the acid, before mixing it up with 

 the gluten. 



Those who have experienced the difficulty of triturating any carbonaceous 

 substance with other vehicles, avUI be surprised at the facility with which a short 

 triture in a mortar unites the materials of this new ink. 



The following tests will enable the Society to judge how it answers the cha- 

 racters which I have ascribed to this composition : 



1. It flows as freely as common ink from the pen. 



2. It speedily becomes sufficiently dry not to be rubbed off' the paper. 



VOL. XIV. PART II. 3 R 



