12. Black oxide of manganese and hydrate of potassa are mixed, heated to redness in a crucible, and then triturated with an equal weight of pure white clay, and water, q. s. to give it due consistence. Used like the last. (Brown.)
13. (Aniline Black Marking Ink.) This ink is prepared by means of two solutions, one of copper, the other of aniline, prepared as follows:—
(1.) Copper solution. 8·52 grams of crystallised chloride of copper, 10·65 grams of chlorate of soda, and 5·35 grams of chloride of ammonium are dissolved in 60 grams of water.
(2.) Aniline solution. 20 grams of hydrochlorate of aniline are dissolved in 30 grams of distilled water, and to this are added 20 grams of solution of gum Arabic (1 part of gum to 2 of water) and 10 grams of glycerin.
By mixing in the cold 4 parts of the aniline solution, with 1 part of the copper solution, a greenish liquid is obtained which can be employed directly for the marking; but as this liquid can only be preserved for a few days without decomposition, it is advisable to keep the solution separately, until the ink is required for use.
The ink may be used either with a pen, or a stencil plate and brush; if it do not flow freely from the pen it may be diluted with a little water without fear of weakening the intensity of the colour. At first the writing appears of a pale green colour, but after exposure to the air it becomes black, or it may be changed to a black colour immediately, by passing a hot iron over the back of the fabric, or heating it over the flame of a spirit lamp. As, however, a dry heat is apt to make the fibre saturated with the ink, brittle, it is preferable to hold the marked fabric over a vessel, containing water in full ebullition; the heat of the vapour is sufficient to determine almost immediately, the reaction by which aniline black is formed. After the steaming, the writing should be washed in hot soapsuds, which
gives the ink a fine blue shade. The ink is not acted upon by acids or alkalies, and if care be taken that the fibres are well saturated with it, there is no danger of its being removed by washing. (‘Dingler’s Journal.’)
14. In addition to the above formulæ, the following of M. Henry may be worthy of attention in large establishments where economy is an object:—Take 1 oz. of iron filings and 3 oz. of vinegar, or diluted acetic acid. Mix the filings with half the vinegar, and agitate them continually till the mixture becomes thick, then add the rest of the vinegar and 1 oz. of water. Apply heat to assist the action, and when the iron is dissolved, add 3 oz. of sulphate of iron, and 1 oz. of gum previously dissolved in 4 oz. of water; and mix the whole with a gentle heat. To be used with brush and stencil plates.
15. (Crimson Marking Ink.) Dissolve 1 oz. of nitrate of silver, and 11⁄2 oz. of carbonate of soda in crystals, separately in distilled water, mix the solutions, collect and wash the precipitate on a filter, introduce the washed precipitate still moist into a Wedgwood mortar, and add to it tartaric acid 2 dr. and 40 gr., rubbing together till effervescence has ceased; dissolve carmine 6 grains, in liquor ammoniæ (·882) 6 oz., and add to it the tartrate of silver, then mix in white sugar, 6 dr., and powdered gum Arabic, 10 dr., and add as much distilled water as will make 6 oz. (‘Pharm. Journal.’)
Obs. The products of the first two of the above formulæ constitute the marking ink of the shops. They have, however, no claim to the title of ‘INDELIBLE INK,’ “which no art can extract without injuring the fabric”—as is generally represented. On the contrary, they may be discharged with almost as much facility as common iron-moulds. This may be easily and cheaply effected by means of ammonia, cyanide of potassium, the chlorides of lime and soda, and some of the hyposulphites, without in the least injuring the texture of the fabric to which they may be applied. The only precaution required is that of rinsing the part in clean water immediately after the operation. The ‘marking ink without preparation’ is more easily extracted than that ‘with preparation.’ The former has also the disadvantage of not keeping so well as the latter, and of depositing a portion of fulminating silver, under some circumstances, which renders its use dangerous. The thinner inks, when intended to be used with type or plates, are thickened by adding a little more gum, or some sugar.