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with ox's blood. It must be applied fresh made, as it soon gets hard.
We believe if the properties of this cement were duly investigated, it would be found useful for many purposes to which it has never yet been applied. It is extremely cheap, and very durable.
Flour paste for cementing is formed principally of wheaten flour boiled in water till it be of a glutinous or viscid consistence.
It may be prepared of these ingredients simply for common purposes, but when it is used by bookbinders, or for paper hangings, it is usual to mix with the flour a fifth or sixth of its weight of powdered alum; and where it is wanted still more tenacious, gum arabic, or any kind of size, may be added.
Japanese Cement, or Rice Glue.
This elegant cement is made by mixing rice flour intimately with cold water, and then gently boiling it. It is beautifully white, and dries almost transparent. Papers pasted together by means of this cement will sooner separate in their own substance than at the joining, which makes it extremely useful in the preparation of curious paper articles, as tea trays, ladies' dressing boxes, and other articles which require layers of paper to be cemented together. It is in every respect preferable to common paste made with wheat flour, for almost every purpose to which that article is usually applied. It answers well in particular, for pasting into books the copies of writings
taken off by copying machines on unsized silver paper.
With this composition, made with a small quantity of water, that it may have a consistence similar to plastic clay, models, busts, statues, basso relievos, and the like, may be formed. When dry, the articles made of it are susceptible of a high polish ; they are also very durable.
The Japanese make quadrille fish of this substance, which so nearly resemble those made of mother of pearl, that the officers of our East Indiamen are often imposed upon.
Common size is manufactured in the same manner, and generally by the same people, as glue. It is indeed glue left in a moister state, by discontinuing the evaporation before it is brought to a dry consistence, and, therefore, further particulars respecting the inanufacture of it are needless here.
Isinglass size may also be prepared in the manner above directed for the glue, by increasing the proportion of the water for dissolving it. And the same holds good of parchment size.
In many chemical operations the vessels must be covered with something to preserve them from the violence of the fire, from being broken or melted, and also to close exactly their joinings to each other, in order to retain the substances which they contain, when they are volatile and
reduced to vapour.
The coating used for retorts, &c. to defend them from the action of the fire, is usually composed of nearly equal parts of coarse sand and refractory clay. These matters ought to be well mixed with water and a little hair, so as to form a liquid paste, with which the vessels are covered layer upon layer, till it is of the required thick
The sand, mixed with the clay, is necessary to prevent the cracks which are occasioned by the contracting of the clay during its drying, which it always does when pure. The hair serves also to bind the parts of the lute, and to keep it applied to the vessel ; for, notwithstanding the sand which is introduced into it, some cracks are al. ways formed, which would occasion pieces of it to fall off.
The lutes with which the joinings of vessels are closed are of different kinds, according to the nature of the operations to be made, and of the substances to be distilled in these vessels.
When vapours of watery liquors, and such as are not corrosive, are to be contained, it is sufficient to surround the joining of the receiver to the nose of the alembic, or of the retort, with slips of paper, or linen, covered with flour paste. In such cases, also, slips of wet bladder are very conveniently used.
When more penetrating and dissolving vapours are to be contained, a lụte is to be employed of quick-lime slacked in air, and beaten into a liquid paste with whites of eggs. This paste is to be spread upon linen slips, which are to be applied exactly to the joining of the vessels. This lute is very convenient, easily dries, becomes solid, and sufficiently firm.
Lastly, when saline acids, and corrosive vapours are to be contained, we must then have recourse to the lute called fat lute. This lute is made by forming into a paste some dried clay, finely powdered, sifted through a silken search, and moistened with water; and then, by beating this paste well in a mortar, with boiled linseed oil, that is, oil which has been rendered dry by litharge dissolved in it, this lute easily takes and retains the form given to it. It is generally rolled into cylinders of a convenient size. These are to be applied, by flattening them to the joinings of the vessels, which ought to be perfectly dry; because the least moisture would prevent the lute from adhering. When the joinings are closed with this fat lute, the whole is to be covered with slips of linen, spread with lutė of lime and whites of eggs. These slips are to be fastened with packthread. The second lute is necessary to keep on the fat lute, because the latter remains soft, and does not become solid enough to stick on alone.
Inks are fluid compounds, intended to form characters, or some other kinds of figures, on proper grounds of paper, parchment, or such other substance as may be fit to receive them.
There are two principal kinds of ink, writing and printing ink.
Writing Ink. When to an infusion of gall-nuts some solution of sulphate of iron (green copperas) is added, a very
dark blue precipitate takes place. This precipitate is the gallic acid of the galls united to the iron of the green vitriol, forming gallat of iron, which is the basis of writing ink. If galls and sulphate of iron only were used, the precipitate would fall down, leaving the water colourless; and, in order to keep it suspended in the water, forming a permanently black, or rather very dark blue fluid, gum arabic is added, which, by its viscid nature, prevents the precipitate from falling down.
Various receipts have been given for the composition of writing ink, but very few have been founded upon a knowledge of its real nature. Though so important an article, it is but lately that it has been studied with any attention; and even still, the principles and theory of its formation do not appear to be so thoroughly understood as might be wished. The receipt given by M. Ribancourt is as follows: Take eight ounces of Aleppo galls, in coarse powder; four ounces of logwood, in thin chips; four ounces of sulphate of iron (green copperas); three ounces of gum arabic, in powder ; one ounce of sulphate of copper (blue vitriol); and one ounce of sugar-candy. Boil the galls and logwood together in twelve pounds of water for one hour, or till half the liquid has been evaporated. Strain the decoction through a hair sieve, or linen cloth, and then add the other ingredients. Stir the mixture till the whole is dissolved, more especially the gum; after which, leave it to subside for twenty-four hours. Then decant the ink, and preserve it in bottles of glass or stone-ware, well corked.
Red writing ink is made in the following manner: Take of the raspings of Brazil wood a quarter of a pound, and infuse them two or three days in vinegar. Boil the infusion for an hour over a gentle