B. WITH LoowooD.—(a) A decoction of logwood is first made by boiling ]0 lb. logwood in enough water to produce 80 lb. of the decoction. To 1000 parts of this logwood extract, when cold, is added 1 part of yellow (neutral) chromate of potash stirring rapidly. It is ready for use at once, without any addition ; but it possesses the great fault of S0011 becoming thick. This may be corrected by (b) adding corrosive sublimate, or any other antiseptic. (c) Boil 10 oz. log wood in 20 oz. water ; then boil again in 20 oz. more water, and mix the two decoctions ; add 2 oz. chrome alum, and boil again for I hour ; add 1 oz. gum arabic. The product is 25 oz. deep black ink. (d) Dissolve 15 parts extract of logwood in 1000 parts distilled water, to which 4 parts carbonate of soda have been added at boiling heat ; and add 1 part neutral chromate of potash dis solved in a little water. This ink will not gelatinize. (e) 10 lb. best logwood is repeatedly boiled in 10 gal. water, straining each time. The liquid is evaporated down till it weighs 100 lb., and is then allowed to boil in a pan of stoneware or enamel. To the boiling liquid, nitrate of oxide of chrome is added in small quantities, until the bronze-coloured precipitate formed at first is redis solved with a deep blue coloration. This solution is then evaporated in a water-bath down to a syrup, with which is mixed well-kneaded clay in the proportion of 1 part of clay to 31 of extract. A little gum tragacanth is also added to obtain a proper consistence. It is absolutely necessary to use the chrome salt in the right proportion. An excess gives a disagreeable appearance to the writing ; while, if too little is used, the black matter is not sufficiently soluble. The other chrome salts cannot be used in this preparation, as they would crystallize, and the writing would scale off as it dried. The nitrate of oxide of chrome is prepared by precipitating a hot solution of chrome alum with carbonate of soda. The precipitate is washed till the filtrate is free from sulphuric acid. The precipitate thus obtained is dissolved in pure nitric acid, so as to leave a little still
undissolved. Hence the solution contains no free acid, which would give the ink a dirty-red colour.
Oxalic acid and caustic alkalies do not attack the writing. Dilute nitric acid reddens, but does not obliterate the charactera. This ink is manufactured into ink-pencils, which give a very black writing, capable of reproduction in the copying-press, and not fading on exposure to light. (f) 20 parts by weight extract of logwood are dissolved in 200 parts water, and the solution is clarified by subsidence and decantation. A yellowish-brown liquid is thus obtained. In another vessel, 10 parts ammonia alum are dissolved in 20 parts boiling water ; the two solutions are mixed, there being also added I- part sulphuric acid, and finally 11 part sulphate of copper. The ink should be exposed to the air for a few days to give it good colour, after which, it should be stored in well corked bottles. (g) 30 parts extract of log wood are dissolved in 250 parts water ; 8 parts crystal lized carbonate of soda, and 30 parts glycerine (sp. gr. 1.25), are added ; lastly, 1 part neutral chromate of potash and 8 parts gum arabic, reduced to a powder, and dissolved in water. This ink does not attack pens, does not turn mouldy, and is very black.
C. MISCELLANEOUS.—(a) The juice or sap of the ink-plant of New Granada, to which is given the name of °halal, is at first of a reddish tint, but in a few hours becomes intensely black. It may be used without any preparation. The chanla corrodes steel pens less than ordinary ink, and better resists the action of time and chemical agents. It is said that, during the Spanish rule, all public documents were required to be written with this ink : written otherwise, they were liable to damage by sea-water. (I) 20 gr. sugar is dissolved in 30 gr. water, and a few drops concentrated sulphuric acid ere added ; the mixture is heated, when the sugar is carbonized by the acid.