This ink will be found excellent for marking, the character will be very black, and it will be found especially useful for applying with the stamp.
Formula No. 3, Nitrate of silver, 17 grammes, Water, 85 grammes, Gum, 20 grammes, Sub-carbonate of soda, 22 grammes, Solution of Ammoniæ, 42 grammes, Sulphate of copper, 33 grammes.
First dissolve the 22 parts of sub-carbonate in the 25 parts of water, and the 15 of nitrate in the 42 of ammonia.
This done, put into the marble mortar the 20 parts of gum with the sixty parts of water which remain, stir it { 108} with the pestle, and pour on it the solution of sub-carbonate, after which, pour the whole into the solution of the nitrate; finish by adding the 33 parts of the solution of sulphate of copper.
The greater quantity of ammonia is explained by the presence of the sulphate to be dissolved.
This composition differs from the others in having a blue tinge, due to the solution of copper.
It will be readily seen that these relative qualities, given as formulæ for the production of suitable inks, may vary according as it is desirable to produce a thicker or thiner ink, or according to the material on which it is to be used, observing that if, on the one hand, the ammonia acts as a solvent, and facilitates the composition of an ink which can be used without a previous preparation; on the other hand, the evaporation of a part of the ammonia by heat, gives to the liquid a dark color which renders the writing immediately black; again, the boiled liquid greases less, and thus penetrates and spreads better on the linen without making a blot.
As to the mode of using, whether with a pen or a stamp proceed as usual, namely: pass a hot iron over the writing, to cause it more completely to penetrate the material.
Considerable attention having of late been directed to this class of compounds, perhaps a few practical observations relating to their manufacture, &c. might be of interest to the readers of _The Annals of Pharmacy_.
Although some of the combinations of valerianic acid with bases, and the properties of those salts, have been described in the books on chemistry, yet I believe I may lay claim to the priority of the preparation of an extensive series of the combination of valerianic acid with bases. { 109}