80 INK appearance which arises through the use of gum. C. H. Viedt of Brunswick, who has written very exhaustively on all kinds of ink, gives the following as the standard in gredients of these three varieties of ink: Galls Ink. Galls-logwood Ink. Galls-Jndigo Ink. Tannin extract, 5 per cent. Ferrous sulphate 1 litre 45 grammes | litre 45 grammes
- 1 litre
Gum senega! 20-30 ,, 20-30 ,, Logwood solution, 3 ( per cent litre Metallic iron 9 grammes Indigo .. . 6i ,, Concentrated sulphuric ) acid 25 Chalk 1 On long exposure to air, as in inkstands, or otherwise, all these varieties of ink gradually become thick and ropy, depositing a slimy sediment. This change on exposure is inevitable, resulting as it does from the gradual and at the same time essential oxidation of the ferrous compound, and it can only be retarded by permitting access of air to as small surfaces as possible. The inks also have a tend ency to become mouldy, an evil which may be obviated by the use of a minute proportion of carbolic acid ; or, should that body be objectionable on account of its smell, salicylic acid may be used. Under the name of chrome ink a black ink was discovered and prepared by the chemist Runge, which held out the promise of cheapness combined with many excellent quali ties. It is prepared by dissolving 15 parts of extract of logwood in 900 parts of water, to which 4 parts of crystal lized sodic carbonate are added. A further solution of 1 part of chromate (not bichromate) of potassium in 100 parts of water is prepared, and is added very gradually to the other solution with constant agitation. Thereby is obtained an ink which possesses an intense blue-black colour, which flows freely and dries readily, which being neutral in reac tion does not corrode steel pens, and which so adheres to and sinks into paper that manuscripts written with it may be freely washed with a sponge without danger of smearing or spreading. It forms a good copying ink, and in short it possesses all the qualities essential to the best ink ; but unfortunately on exposure to air it very readily undergoes decomposition, the colouring matter separating in broad flakes, which swim in a clear menstruum. It is affirmed by Viedt that this drawback may be overcome by the use of soda, a method first suggested by Bottger. Logwood forms the principal ingredient in various other black inks which are now much used, especially as copying ink. A very strong decoction of logwood or a strong solu tion of the extract with ammonia-alum yields a violet ink which darkens slowly on exposure. Such an ink is costly, however, on account of the concentrated condition in which the logwood must be used. If, however, a metallic salt is introduced, a serviceable ink is obtained with the expendi ture of much less logwood. Either sulphate of copper or sulphate of iron may be used, but the former, which pro duces a pleasing blue-black colour, is to be preferred. The following is the formula most highly recommended for this ink. A clear solution of 20 kilos of extract of logwood in 200 litres of water is obtained, to which is added, with agitation, 10 kilos of ammonia-alum dissolved in 20 litres of boiling water. The solution is acidified with 2 kilo of sulphuric acid, which has the effect of preventing any deposit, and finally there is added a solution of 1 5 kilos of sulphate of copper dissolved in 20 litres of water. This compound is exposed to the air for a few days to allow the colour to develop by oxidation, after which it is stored in well-corked bottles. The acid condition of this ink has a corrosive influence on steel pens ; but in all other respects it is a most valuable writing fluid. A black ink under the name of nigrosin is prepared from a soluble aniline colour, which, although not producing a black so intense as common ink, is possessed of various advantages. Being perfectly neutral, it does not attack pens; it can easily be kept of a proper consistency by making up with water ; and its colour is not injuriously affected by the action of acids. Copying Ink. Ink which yields by means of pressure an im* pression, on a sheet of damped tissue paper, of characters written in it is called copying ink. Any ink soluble in water, or which retains a certain degree of solubility, may be used as copying ink. Runge s chrome ink, being a soluble compound, is, therefore, so available ; and the other logwood inks as well as< the ordinary ferrous gallate inks contain also soluble constituents, and indeed are essentially soluble till they are oxidized in and on the paper after exposure to the air. To render these available as copying inks it is only necessary to add to them a substance which will retard the oxidizing effect of the air for some time. For this purpose the bodies most serviceable are gum arabic or Senegal, with glycerin, dextrin, or sugar, which last, however, has the disadvantage of rendering the ink sticky. These substances act by forming a kind of glaze or varnish over the surface of the ink which excludes the air. At the same time when the damp sheet of tissue paper is applied to the writing they dissolve and allow a portion of the yet soluble ink to be absorbed by the moistened tissue. As copying ink has to yield two or more impressions, it is necessary that it should be made stronger, i.e., that it should contain more pig ment or body than common ink. It, therefore, is prepared with from 30 to 40 per cent, less of water than non-copying kinds ; but otherwise, except in the presence of the ingredients above alluded to, the inks are quite the same. Ecd Ink. The pigment most commonly employed as the basis of red ink is Brazil-wood, a dye-stuff which yields a good durable ink. Such an ink is prepared by adding to a strong decoction of the wood a proportion of stannous chloride (tin spirits), and thickening the resulting fluid with gum arabic. In some instances alum and cream of tartar are used instead of the stannous chloride. Cochineal is also employed as the tinctorial basis of red ink ; but, while the re sulting fluid is much more brilliant than that obtained from Brazil wood, it is not quite so permanent. A very brilliant red ink may be prepared by dissolving carmine in a solution of caustic ammonia, but it is necessary to keep this preparation in closely stoppered bottles. A useful red ink may also be made by dissolving the roseLn of Brooke, Simpson, and Spiller in water, in the proportion of 1 to from 150 to 200 parts. Blue Ink. For the production of blue ink the pigment princi pally used is Prussian blue. To render this colour soluble in water it is first digested for two or three days with either strong hydro chloric acid, sulphuric acid, or nitric acid, the digested mass is next very largely diluted with water, and after settling the supernatant liquid is siphoned away from the sediment. This sediment is repeatedly washed, till all traces of iron and free acid disappear from the water used, after which it is dried and mixed with oxalic acid in the proportion of 8 parts of Prussian blue to 1 of the acid, and in this condition the material is ready for dissolving in water to the degree of colour intensity necessary. An aniline blue ink may be prepared by dissolving 1 part of bleu de Paris in from 200 to 250 parts of water. China ink or Indian ink is the form in which ink was earliest prepared, and in which it is still made and used in China and Japan for writing with small brushes instead of pens. It is exten sively used by architects, engineers, and artists generally, and for various special uses. China ink is prepared in the form of sticks and cakes, which are rubbed down in water for use. It consists essentially of lamp-black in very fine condition, baked up with a glutinous substance ; and the finer Oriental kinds are delicately per fumed. The following description of the manufacture as conducted in Japan is from a native source : " The body of the ink is soot obtained from pine wood or rosin, and lamp-black from sesamum oil for the finest sort. This is mixed with liquid glue made of ox skin. This operation is effected in a large round copper bowl, formed of two spherical calottes, placed 1 inch apart, so that the space be tween can be filled up with hot water to prevent the glue from hardening during the time it is being mixed by hand with the lamp-black. The cakes arc formed in wooden moulds, and dried between paper and ashes. Camphor, or a peculiar mixture of scents which comes from China, and a small quantity of carthamine (the red colouring substance of safllower), are added to the best kinds for Improving the colour as well as for scenting the ink. There is a great difference both in price and in quality of the various kinds of ink, the finest article being rather costly." It is said that the size used in Chinese kinds is of vegetable origin.
