Cooley's Cyclopaedia of Practical Receipts Volume I Part 217

The fluids employed for 'biting in' the designs vary considerably, almost every artist having his own receipt. Aquafortis, more or less diluted, is, however, generally employed for COPPER, and this, with the addition of pyroligneous acid, for etching on STEEL; but any fluid that rapidly dissolves the metal may be used for the purpose. The 'etching ground' may be formed of any substance capable of resisting the action of the etching fluid, and which is, at the same time, sufficiently soft to allow of the free use of the needle or point, and sufficiently solid to prevent an injury to the design during the 'scratching in,'

In ETCHING ON GLa.s.s, the ground is laid on, and the design 'scratched in'

in the usual way, when liquid hydrofluoric acid is applied, or the gla.s.s is exposed to the action of hydrofluoric acid gas. The former renders the surface of the etching transparent, the latter opaque. A simple modification of the process is to wet the design with sulphuric acid, and then to sprinkle on some finely pulverised fluor spar (fluoride of calcium), by which means hydrofluoric acid is set free and attacks the gla.s.s. This method may be very easily applied to the graduation of gla.s.s vessels, thermometer tubes, &c.

ETCHING ON GLa.s.s BY ELECTRICITY. Plante ('Ann. Chem. Phys.' [5], xiii, 143-144). The author had previously drawn attention to the fact that when an electric current is pa.s.sed through saline solutions in gla.s.s vessels, platinum wire serving as electrodes, the gla.s.s is immediately attacked, and he therefore proposes the following method for etching on gla.s.s:

The surface of the gla.s.s to be engraved is coated with a concentrated solution of pota.s.sium nitrate, and beneath the layer of liquid a platinum wire, connected with one of the poles of a battery, is stretched across the plate. With the other pole is connected another platinum wire, the whole of which, except the point, is insulated; with this the designs are drawn on the gla.s.s, which is engraved wherever the wire comes in contact with it, flashes of light being emitted at the same time.

The depth of engraving depends on the rate at which the platinum wire moves; the slower the rate the deeper the line.

A RAPID METHOD OF ETCHING ON IRON OR STEEL, capable of very general application, is as follows:--"The metal is warmed until it is capable of melting a piece of beeswax, or 'etching ground,' which is then carefully rubbed over it, so as to form a thin and even coating; when cold, the design is 'scratched in' in the common way; a little powdered iodine is then sprinkled on the exposed parts, and at the same time a few drops of water are added, and the two worked into a liquid paste with a camel-hair pencil. The paste is then moved about over the intended etching, for a period varying from one to five minutes, according to the depth of the lines required to be produced. Afterwards the whole is removed, and reapplied, &c., as with the usual etching fluids. The same etching-paste, by being kept for a few days, again acquires the property of dissolving iron, and may be used again and again; but independently of this, the iodide of iron formed during the process, if rapidly evaporated to dryness in a clean iron vessel by a moderate heat, and placed in stoppered bottles, will sell for more than the original cost of the iodine. To travellers and amateurs who amuse themselves with the delightful art of etching, iodine, from its portability and convenience, will, doubtless, prove invaluable. We have adopted it with considerable success, and have found it especially useful in marking surgical instruments, razors, and other edge tools. We published this method many years ago. Several parties have since availed themselves of our suggestions and formulae, but without the slightest acknowledgment of the source from which they obtained them."

(A. J. Cooley.)

=Etching, Electro-.= This mode of etching, which is in many respects superior to the ordinary mode, is based upon the destructive action of certain 'anions' during 'electrolysis.'[281] If two plates of copper be connected with the opposite ends of a voltaic battery, and placed in a vessel containing very dilute sulphuric acid, the plate connected with the copper of the battery will be attacked by the anion oxygen which is released during the decomposition of the acid. This destructive action can be localised at pleasure by covering certain parts of the plate with a protecting stratum of varnish, ordinary 'etching ground' for instance. In the practice of electro-etching, the drawing is 'scratched in' in the usual way through an ordinary ground; a stout wire is then soldered to the plate, and this, as well as the back of the plate, is coated with sealing-wax varnish. Thus prepared, the plate is placed in a suitable 'decomposition cell' opposite a plate of somewhat similar size, and the two are connected respectively with the copper and zinc of a 'Daniell's cell,' or the silver and zinc of a 'Smee's cell.'[282] After about ten minutes the plate is removed, washed, and dried; and when the 'fine work'

has been stopped out with Brunswick black, it is returned for another s.p.a.ce of ten minutes. By alternately exposing the plate to the action of the decomposing fluid, and 'stopping out' parts of the work, the required gradation in tints is obtained. The exact duration of the various exposures, as well as their number, must, of course, be regulated by circ.u.mstances. See ETCHING FLUIDS (_below_).

[Footnote 281: See ELECTROLYSIS and ELECTROTYPE, pages 428 and 429.]

[Footnote 282: See VOLTAIC ELECTRICITY.]

=Etching Fluids.= 1. (For COPPER.)--_a._ From 'aquafortis,' 2-1/2 fl. oz.; water, 5 fl. oz.; mix.

_b._ To the last add of verdigris, 1 oz.; water, 2-1/2 fl. oz.; dissolve.

For light touches.

_c._ (EAU FORTE,--Callot and Piranesi.) Alum, sal-ammoniac, sea salt, and verdigris, of each 4 oz.; vinegar (pyroligneous acid), 8 fl. oz.; water, 16 fl. oz.; mix, dissolve, boil for 1 or 2 minutes in a glazed or stoneware vessel, cool, and decant the clear portion. Used as the last.

_d._ Water acidulated with sulphuric acid. Used in the process of electro-etching.

2. (For STEEL.)--_a._ From iodine, 1 oz.; iron filings or wire, 1/2 dr.; water, 4 fl. oz. It must be kept in a stoppered bottle, until required for use.

_b._ From iodine, 3 dr.; iodide of pota.s.sium, 1 dr.; proof spirit, 1 fl.

oz.; water, 2 fl. oz. As the last.

_c._ (Mr Turrel.) Pyroligneous acid, 4 fl. oz.; alcohol (rectified spirit), 1 fl. oz.; mix, and add of nitric acid or double aquafortis (sp.

gr. 128), 1 fl. oz.

_d._ From hydrochloric acid, 5 parts; water, 95 parts; mix, and add the liquid to a solution of chlorate of pota.s.sa, 1 part, in water, 50 parts.

_e._ A solution of common salt. Used in the process of electro-etching.

=Etching Ground.= _Syn._ ETCHING VARNISH. _Prep._ 1. Beeswax, 5 parts; linseed oil, 1 part; melted together.

2. (Callot's HARD VARNISH, FLORENTINE V., FLORENCE V.) From linseed oil and mastic, equal parts, melted together.

3. (Callot's SOFT VARNISH.) From linseed oil, 4 oz.; gum benzoin and white wax, of each 1/2 oz.; boil to two thirds.

4. (Lawrence.) White wax, 2 oz.; black pitch and Burgundy pitch, of each 1/2 oz.; melt, add by degrees, of powdered asphaltum, 2 oz.; and boil together, until a piece, when thoroughly cold, will break by being bent double 2 or 3 times between the fingers; next pour it into warm water, make it into small b.a.l.l.s, and place each of them in a piece of taffety for use.

_Obs._ The preceding compositions are applied to the surface of the plates, previously made sufficiently warm to melt them easily, their even diffusion being promoted by dabbing them with a wad of cotton. Those that are white are then generally blackened on the surface by skilfully pa.s.sing them over the smoky flame of one or more candles, by which the marks of the etching point on the bright metal are rendered the more visible.

=E'THER.= _Syn._ OXIDE OF ETHYL. Described under ETHYL, OXIDE OF. Several substances are known under the name of ethers besides the true ethers or salts of ethyl, and are given below.

=Ether of Canthar'ides.= _Syn._ aeTHER CANTHARIDALIS, L. _Prep._ (ttinger.) From powdered cantharides, 1 part; ether, 2 parts; digested together for 3 or 4 days, and the tincture expressed. Used as a vesicant, &c.

=Ether, Chlo"ric.= This name was applied by Dr T. Thomson to the CHLORIDE OF OLEFIANT GAS, or 'DUTCH LIQUID,' and afterwards, by Guthrie and Silliman, to CHLOROFORM, which they took for an alcoholic solution of chloride of olefiant gas. It now forms one of the synonyms of chloroform.

The medicinal 'CHLORIC ETHER' of the shops is a solution of chloroform, 1 part, in rectified spirit 8 parts; of which the _dose_ is 20 or 30 drops in water, as an antispasmodic and anodyne. See CHLOROFORM.

=Ether, Chlorinet'ted.= Formed by the action of dry chlorine on pure ether. When the action is long continued, a heavy, oily product (b.i.+.c.hLORINETTED ETHER), smelling like fennel, is formed. By the still further action of chlorine, aided by sunlight, a white, crystalline substance (PENTACHLORINETTED ETHER), a compound resembling sesquichloride of carbon, is obtained.

=Ether, Cu"preous.= _Syn._ TINCTURA CUPRI CHLORIDI aeTHEREA, L. _Prep._ (Van Mons.) Sulphate of copper, 6 parts, and chloride of barium, 5 parts, are triturated together, and the mixture digested in ether, 3 or 4 parts, until all the chloride of copper is dissolved.--_Dose_, 2 to 5 drops; in epilepsy, &c.

=Ether, Methy'lic.= _Syn._ OXIDE OF METHYL, WOOD-ETHER, METHYL-ETHER; aeTHER METHYLICUS, L. _Prep._ From wood spirit, 1 part; concentrated sulphuric acid, 4 parts; mix in a retort, apply heat, pa.s.s the evolved gas (methylic ether) through a little strong solution of pota.s.sa, and then collect it over mercury. See METHYL.

=Ether, Spirits of Nitrous.= See SPIRITS.

=Ether, Washed.= _Syn._ aeTHER LOTUS, L. Ordinary ether, agitated first with 2 or 3 times its volume of distilled water, and a few grains of carbonate of pota.s.sa, or a few drops of milk of lime; and after decantation, again agitated with a like quant.i.ty of water only. Used for inhalations. For other purposes the washed ether is afterwards digested on chloride of calcium, to deprive it of retained water.

=E'THERIN.= _Syn._ CAMPHOR OF OIL OF WINE. A volatile, white, crystalline substance, deposited by light oil of wine when left in a cold situation for some time. It is isomeric with etherole, and received its name from the a.s.sumption of its being the base of the ethereal compounds. According to this hypothesis, ether is a hydrate of etherin. Etherin forms brilliant prisms and plates; is tasteless; soluble in alcohol and ether; fuses at 230 Fahr., and boils at 500 Fahr.; and is a little lighter than water.

The crystals are purified by pressure between the folds of bibulous paper, solution in ether, and evaporation.

=E'THEROLE.= The yellowish, oily liquid, forming the residual portion of light oil of wine, after it has deposited its etherin. It is lighter than water; is freely soluble in both alcohol and ether; and has a rather high boiling-point. See ETHERIN and OIL OF WINE.

=ETHION'IC AC'ID.= _Prep._ An alcoholic solution of the crystals of sulphate of carbyle is diluted with water, the whole neutralised with carbonate of baryta, the filtered liquid evaporated by a very gentle heat to a small bulk, and a large quant.i.ty of alcohol added; the precipitate (ethionate of baryta) is treated (cautiously) with dilute sulphuric acid (avoiding excess), by which the baryta is withdrawn, and ethionic acid left in solution.

_Prop., &c._ Ethionic acid closely resembles sulphovinic acid. It is decomposed by heat. Its salts (ethionates), however, differ completely from the sulphovinates. They are all soluble in water, and are said to be anhydrous. The ethionates of ammonia, pota.s.sa, and soda crystallise readily; those of lead, baryta, lime, and the other earths are uncrystallisable. See ISETHIONIC ACID, and _below_.

=ETHION'IC ANHY'DRIDE.= _Prep._ Pure and dry olefiant gas is pa.s.sed over anhydrous sulphuric acid ('sulphuric anhydride') contained in a U-shaped tube.

_Prop., &c._ When thus produced, it is in white, milky crystals, which speedily deliquesce in the air, giving rise to ethionic acid. It is similar in appearance, and probably identical with, 'sulphate of carbyle,'

which results from the absorption of the vapour of anhydrous sulphuric acid by absolute alcohol.

=E'THIOPS.= _Syn._ aeTHIOPS, L. A name given by the older chemists to several black powders on account of their colour, and still occasionally employed in medical works.

=Ethiops, Graphi'tic.= _Syn._ ETHIOPS OF PLUMBAGO; aeTHIOPS GRAPHITICUS, L.

From plumbago, 2 parts; quicksilver, 1 part; triturated together until the globules disappear.--_Dose_, 5 to 10 gr.; in herpes, and some other obstinate skin diseases.

=Ethiops, Martial.= Black oxide of iron, prepared by keeping iron filings under water, and occasionally shaking them. It is washed with water, dried as quickly as possible, and preserved from the air, to prevent further oxidation. Formerly much esteemed as a tonic.

=Ethiops, Min'eral.= _Syn._ ETHIOPS MINERAL; aeTHIOPS MINERALIS, HYDRARGYRI SULPHURETUM c.u.m SULPHURE, L. Black sulphuret of mercury, with excess of sulphur.

(Tyson's.) Oxide of mercury (prepared by decomposing calomel with an equivalent proportion of liquor of pota.s.sa to which a little liquor of ammonia has been added) and flowers of sulphur, equal parts, triturated together. This is recommended as an efficient subst.i.tute for the old and uncertain preparation commonly sold under the name of _Ethiops mineral_.

It is, however, of more than double the usual strength, and should therefore be taken in proportionate doses. See MERCURY (Sulphide).

=Ethiops, Veg'etable.= _Syn._ aeTHIOPS VEGETABILIS, PULVUS QUERCS MARINae, L. Bladder wrack (_Fucus vesiculosus_), burned in a close vessel till it becomes black and friable. Used in bronchocele, scrofula, &c. Like burnt sponge, it owes its virtues to the presence of a very minute quant.i.ty of iodine.--_Dose_, 20 gr. to 1 dr., or more, made into an electuary with honey or sugar.

=E'THYL.= C_{2}H_{5}. _Syn._ ETHYLE. The hydrocarbon a.s.sumed to be the radical of the ether-compounds (ethyl-series). A body containing carbon and hydrogen in the proportions indicated by the formula of ethyl, 2(C_{2}H_{5}), has been obtained by exposing dry iodide of ethyl in sealed tubes for several hours to the action of finely divided zinc, at a temperature of from 320 to 338 Fahr. In this reaction the iodine of the iodide of ethyl combines with the zinc, and the hydrocarbon supposed to be ethyl is set free. On opening the sealed tubes and allowing the gas (which is a mixture of the 'ethyl' and certain secondary products) to pa.s.s into a freezing mixture, the temperature of which is kept below -9 Fahr., the 'ethyl' condenses to a colourless, mobile liquid. Hitherto no compound ether has been produced from the 'ethyl' thus prepared.