914 INK 



INDIGO-COPPER. The native protosulphide of copper, known also as CoveUine. 



INDIGO-GREEN. A green substance obtained from indigo by adding potash 

 to an alcoholic solution of an alkaline hyposulph-indigotate. 



INDlGO-PITRPIiX:. Finely-powdered indigo is added to twenty times it weight 

 of acid sulphate of soda in a state of fusion, and the mixture is heated and stirred 

 till a sample colours water violet. The paste thus produced is then intimately mixed 

 with 70 or 80 times. its weight of water, and the colouring matter is precipitated by 

 common salt and washed with saline water. After drying it forms a mass of inter- 

 laced silky crystals having a coppery lustre. 



INDIGO-RED. A red substance found in commercial indigo. For particulars 

 relative to this and other indigo colours, consult Watts's ' Dictionary of Chemistry,' 

 and the authorities there quoted. 



INDISINE. See ANILINE-VIOLET. 



INDIUM. This metal was discovered in 1863, by Professors Keich and Richter, 

 who detected it, by the aid of spectrum analysis, in the zinc-blende of Freiberg in 

 Saxony. The spectrum of salts of indium is characterised by two indigo-blue lines, 

 one very bright, and the other fainter. Indium is a soft, malleable, lead-grey metal, 

 of specific gravity 7'2. The atomic weight is believed to be 74. The metal is readily 

 soluble in hydrochloric acid, forming a deliquescent chloride of indium. The salts 

 of indium have hitherto been but imperfectly studied, and none of them have yet 

 found any application in the arts. 



INGRAIN. Wools, &c., are said to be dyed ingrain when they are subjected to 

 that process before manufacture. 



INK. (Encre, Fr. ; Tinte, Ger.) 



Writing Ink may be and is prepared in many different ways ; but it is essentially a 

 tanno-gallate of iron. 



Nut-galls, sulphate of iron, and gum are the only substances truly useful in the 

 preparation of ordinary ink ; the other things, often added, merely modify the shade 

 and considerably diminish the cost to the manufacturer upon the great scale. Many 

 of these inks contain little gallic acid or tannin, and are therefore of inferior quality. 

 To make 12 gallons of ink, we may take 12 pounds of nut-galls, 5 pounds of green 

 sulphate of iron, 5 pounds of gum Senegal, 12 gallons of water. The bruised 

 nut-galls are to be put into a cylindrical copper, of a depth equal to its diameter, and 

 boiled during three hours, with three-fourths of the above quantity of water, taking 

 care to add fresh water to replace what is lost by evaporation. The decoction is to 

 be emptied into a tub, allowed to settle, and the clear liquid being drawn off, the lees 

 are to be drained. The gum is to be dissolved in a small quantity of hot water, and the 

 mucilage thus formed, being filtered, is added to the clear decoction. The sulphate 

 of iron must likewise be separately dissolved, and well mixed with the above. The 

 colour darkens by degrees, in consequence of the peroxidation of the iron, on ex- 

 posing the ink to the action of the air. But ink affords a more durable writing when 

 used in the pale state, because its particles are then finer and penetrate the paper more 

 intimately. When ink consists chiefly of tannate of peroxide of iron, however black, 

 it is merely superficial, and is easily erased or effaced. Therefore, whenever the 

 liquid made by the above recipe has acquired a moderately deep tint, it should bo 

 drawn off clear into bottles and well corked up. Some ink-makers allow it to mould 

 a little in the casks before bottling, and suppose that it will thereby be not so liable to 

 become mouldy in the bottles. 



From the comparatively high price of gall-nuts, sumach, logwood, and even oak 

 bark are too frequently substituted, to a considerable degree, in the manufacture of 

 ink ; but always injuriously. 



The ink made by the recipe given above, is much more rich and powerful than many of 

 the inks commonly sold. To bring to their standard a half more water may safely bo 

 added, or even twenty gallons of tolerable ink may be made from that weight of materials. 



Sumach and logwood admit of only about one half of the copperas that galls will 

 take to bring out the maximum amount of black dye. 



Lewis, who made exact experiments on inks, assigned the proportion of throe parts 

 of galls to one of sulphate of iron, which, with average galls, will answer very well ; 

 but good galls will admit of more copperas. 



Red Ink. This ink may be made by infusing for three or four days in weak 

 vinegar, Brazil wool chipped into small pieces ; the infusion may then be boiled 

 upon the wood for an hour, strained and thickened slightly with gum arabir ami 

 sugar. A little alum improves the colour. A decoction of cochineal with a littlo 

 water of ammonia, forms a more beautiful red ink, but it is fugitive. An extem- 

 poraneous red ink of the same kind may bo made by dissolving carmine in weak 

 water of ammonia, and adding a little mucilage. 



Blue Ink. Mr. Stephens's patent blue ink is made by dissolving Prussian blue in 



