The following is said to be the Dutch mode of making Geneva:

One cwt. of barley malt and two cwts. of rye meal are mashed with 460 gallons of water, heated to 162°F. After the farine have been infused for a sufficient time, cold water is added, till the wort becomes equivalent to 45 pounds of saccharine matter per barrel. Into a vessel of 500 gallons capacity, the wort is now put at the temperature of 80°, with half a gallon of yeast. The fermentation instantly begins, and is finished in 48 hours, during which the heat rises to 90°. The wash, not reduced lower than 12 or 15 pounds per barrel, is put into the still along with the grains. Three distillations are required; and at the last, a few juniper berries and hops are introduced to communicate flavour. The attenuation of 45 pounds in the wort, to only 15 in the wash shows that the fermentation is here very imperfect and uneconomical; as indeed we might infer from the small proportion of yeast, and the precipitancy of the process of fermentation. On the other hand, the very large proportion of porter yeast in a corrupting state, used by the Scotch distillers, cannot fail to injure the flavour of their spirits.

Rum is obtained from the fermentation of the coarsest sugar and molasses in the West Indies, dissolved in water in the proportion of nearly a pound to the gallon. The yeast is procured chiefly from the rum wort. The receding details s give sufficient instruction for the conduct of this modification of the process.

Sykes' hydrometer is now universally used in the collection of the spirit revenue in Great Britain. It consists, first of a flat stem, 3.4 inches long, which is divided on both sides into 11 equal parts, each of which is subdivided into two, the scale being numbered from 0 to 11. This stem is soldered into a brass ball 1.6 inch in diameter, into the under part of which is fixed a small conical stem 1.13 inch long, at whose end is a pear-shaped loaded bulb, half an inch in diameter. The whole instrument, which is made of brass, is 6.7 inches long. The instrument is accompanied with 8 circular weights, numbered 10, 20, 30,40,50,60,70, 80, and another weight of the form of a parallelopiped. Each of the circular weights is cut into its centre, so that it can be placed on the inferior conical stem, and slid down to the bulb; but in consequence of the enlargement of the cone, they cannot slip off at the bottom, but must be drawn up to the thin part for this purpose. The square weight of the form of a parallelopiped, has a square notch in one of its sides, by which it can be placed on the summit of the stem. In using this instrument, it is immersed in the spirit, and pressed down by the hand to O, till the whole di

vided part of the stem be wet. The force of the hand required to sink it, will be a guide in selecting the proper weight. Having taken one of the circular weights, which is necessary for this purpose, it is slipped on the conical stem. The instrument is again immersed and pressed down as before to O, and is then allowed to rise and settle, at any point of the scale. The eye is then brought to the level of the surface of the spirit, and the part of the stem cut by the surface, as seen from below, is marked. The number thus indicated by the stem is added to the number of the weight employed, and with this sum at the side, and the temperature of the spirits at the top, the strength per cent is found in a table of 6 quarto pages. "The strength is expressed in numbers denoting the excess or deficiency per cent of proofspirit in any sample, and the number itself (having its decimal point removed two places to the left) becomes a factor, whereby the gauged content of a cask or vessel of such spirit being multiplied, and the product being added to the gauged content, if over proof, or deducted from it if under proof, the result will be the actual quantity of proof spirit contained in such cask or vessel."*

*DISTHENE. See CYANITE.*

* DISTINCT CONCRETIONS. A term in

MINERALOGY.*

DOCIMASTIC ART. This name is given to the art of assaying. See ASSAY, BLOWPIPE, ANALYSIS, and the several metals. *DOLOMITE. Of this calcareo-magnesian carbonate, we have three sub-species 1. Dolomite, of which there are two kinds. §1st. Granular Dolomite.

White granular. It occurs massive, and in fine granular distinct concretions, loosely aggregated. Lustre glimmering and pearly. Fracture in the large, imperfect slaty. Faintly translucent. As hard as fluor. Brittle Sp. gr. 2.83. It effervesces feebly with acids. Phosphorescent on heated iron, or by friction. Its constituents are 46.5 carbonate of magnesia, 52.08 carbonate of lime, 0.25 oxide of manganese, and 0.5 oxide of iron. Klaproth. Beds of dolomite, containing tremolite, occur in the island of Iona, in the mountain group of St. Gothard, in the Appenines, and in Carinthia. A beautiful white variety used by ancient sculptors, is found in the Isle of Tenedos. Jameson.

The flexible variety was first noticed in the Borghese palace at Rome; but the other varieties of dolomite, and also common granular limestone, may be rendered flexible, by exposing them in thin and long slabs to a heat of 480° Fahr. for 6 hours.

§2d, Brown Dolomite, or magnesian lime stone of Tennant.

Colour, yellowish-gray and yellowishbrown. Massive, and in minute granular

concretions. Lustre internally glistening. Fracture splintery. Translucent on the edges. Harder than calcareous spar. Brittle. Sp. gr. of crystals, 2.8. It dissolves slowly, and with feeble effervescence; and when calcined, it is long in re-absorbing carbonic acid from the air. Its constituents are, lime 29.5, magnesia 20.3, carbonic acid 47.2. Alumina and iron 0.8. Tennant. In the north of England it occurs in beds of considerable thickness, and great extent, resting on the Newcastle coal formation. In the Isle of Man, it occurs in a limestone which rests on gray-wacke. It occurs in trap-rocks in Fifeshire. When laid on land after being calcined, it prevents vegetation, unless the quantity be smalll.

To the preceeding variety we must refer a flexible dolomite found near Tinmouth Castle. It is yellowish-gray, passing into creamyellow. Massive. Dull. Fracture earthy. Opaque. Yields readily to the knife. In thin plates, very flexible. Sp. gr. 2.54; but the stone is porous. It dissolves in acids as readily as common carbonate of lime. Its constituents are said to be 62 carbonate of lime, and 36 carbonate of magnesia. When made moderately dry, it loses its flexibility; but when either very moist or very dry, it is very flexible.

2d, Columnar Dolomite. Colour pale grayish-white. Massive, and in thin prismatic concretions. Cleavage imperfect. Fracture uneven. Lustre vitreous, inclining to pearly. Breaks into acicular fragments. Feebly translucent. Brittle. Sp. gr. 2.76. Its constituents are 51 carbonate of lime, 47 carbonate of magnesia, 1 carbonated hydrate of iron. It occurs in serpentine in Russia.

3d, Compact Dolomite, or Gurhofite. Colour snow-white. Massive. Dull. Fracture flat conchoidal. Slightly translucent on the edges. Semi-hard. Difficultly frangible. Sp. gr 2.76. When pulverized, it dissolves with effervescence in hot nitric acid. It consists of 70.5 carbonate of lime, and 29.5 carbonate of magnesia. It occurs in veins in serpentine rocks, near Gurhoff, in Lower Austria.*

CURY.*

DRACO-MITIGATUS. Calomel. See MER* DRAGON'S BLOOD. A brittle dark red coloured resin, imported from the East Indies, the product of pterocarpus draco, and dracæna draco. It is insoluble in water, but soluble in a great measure in alcohol. The solution imparts a beautiful red stain to hot marble. It dissolves in oils. It contains a little benzoic acid.*

*DRAWING SLATE. Black chalk. Colour grayish black. Massive. Lustre of the principal fracture, glimmering; of the cross fracture, dull. Fracture of the former slaty, of the latter, fine earthy. Opaque. It writes. Streak same colour, and glis

tening. Very soft. Sectile. Easily frangible. It adheres slightly to the tongue,Feels fine, but meagre. Sp. gr. 2.11. It is infusible. Its constituents are, silica 64.06, alumina 11, carbon 11, water 7.2, iron 2.75 It occurs in beds in primitive and transition clay-slate, also in secondary formations. It is found in the coal formation of Scotland, and in most countries. It is used in crayonpainting. The trace of bituminous shale is brownish and irregular; that of black chalk is regular and black. The best kind is found in Spain, Italy, and France.*

DUCTILITY. That property or texture of bodies, which renders it practicable to draw them out in length, while their thickness is diminished without any actual fracture of their parts. This term is almost exclusively applied to metals.

Most authors confound the words malleability, laminability, and ductility together, and use them in a loose indiscriminate way; but they are very different. Malleability is the property of a body which enlarges one or two of its three dimensions, by a blow or pressure very suddenly applied. Laminability belongs to bodies extensible in dimension by a gradually applied pressure. And ductility is pro properly to be attributed to such bodies as can be rendered longer and thinner by drawing them through a hole of less area than the transverse section of the body

so drawn.

DYEING. The art of dyeing consists in fixing upon cloths of various kinds any colour which may be required, in such a manner as that they shall not be easily altered by those agents, to which the cloth will most probably be exposed.

As there can be no cause by which any colouring matter can adhere to any cloth, except an attraction subsisting between the two substances, it must follow, that there will be few tinging matters capable of indelibly or strongly attaching themselves by simple application.

Dyeing is therefore a chemical art.

The most remarkable general fact in the art of Dyeing, consists in the different degrees of facility, with which animal and vegetable substances attract and retain colouring matter, or rather the degree of facility with which the dyer finds he can tinge them with any intended colour. The chief materials of stuff to be dyed are wool, silk, cotton, and linen, of which the former two are more easily dyed than the latter. This has been usually attributed to their greater attraction to the tinging matter.

Wool is naturally so much disposed to combine with colouring matter, that it requires but little preparation for the immediate process of dyeing; nothing more being required than to cleanse it, by scouring, from a fatty substance, called the yolk, which is contained in the fleece. For this purpose an alkaline liquor is necessary; but as alkalis injure the texture of the wool, a very weak solution may be used. For if more alkali were present than is sufficient to convert the yolk into soap, it would attack the wool itself. Putrid urine is therefore generally used, as being cheap, and containing a volatile alkali, which, uniting with the grease, renders it soluble in water. Silk, when taken from the cocoon, is covered with a kind of varnish, which, because it does not easily yield either to water or alcohol, is usually said to be soluble in neither. It is therefore usual to boil the silk with an alkali, to disengage this matter. Much care is necessary in this operation, because the silk itself is easily corroded or discoloured. Fine soap is commonly used, but even this is said to be detrimental; and the white China silk, which is supposed to be prepared without soap, has a lustre superior to that of Europe. Silk loses about one-fourth of its weight by being deprived of its varnish. See BLEACH

ING.

The intention of the previous preparations seems to be of two kinds. The first to render the stuff or material to be dyed as clear as possible, in order that the aqueous fluid to be afterward applied, may be imbibed, and its contents adhere to the minute internal surfaces. The second is, that the stuff may be rendered whiter and more capable of reflecting the light, and consequently enabling the colouring matter to exhibit more brilliant tints.

Some of the preparations, however, though considered merely as preparative, do really constitute part of the dyeing processes themselves. In many instances a material is applied to the stuff, to which it adheres; and when another suitable material is applied, the result is some colour desired. Thus we might dye a piece of cotton black, by immersing it in ink; but the colour would be neither good nor durable, because the particles of precipitated matter, formed of the oxide of iron and acid of galls, are already concreted in masses too gross either to enter the cotton, or to adhere to it with any considerable degree of strength. But if the cotton be soaked in an infusion of galls, then dried, and afterward immersed in a solution of sulphate of iron (or other ferruginous salt), the acid of galls being every where diffused through the body of the cotton, will receive the particles of oxide of iron, at the very instant of their transmission from the finid, or dissolved to the precipitated or solid state, by which means a perfect covering of the black inky matter will be applied in close contact with the surface of the most minute fibres of the cotton. This dye will therefore not VOL. I.

only be more intense, but likewise more adherent. and durable.

The French dyers, and after them the English, have given the name of mordant to those substances which are previously applied to piece goods, in order that they may afterward take a required tinge or dye.

It is evident, that if the mordant be universally applied over the whole of a piece of goods, and this be afterward immersed in the dye, it will receive a tinge over all its surface; but if it be applied only in parts, the dye will strike in those parts only. The former process constitutes the art of dyeing, properly so called; and the latter, the art of printing woollens, cottons, or linens, called calico-printing.

In the art of printing piece goods, the mordant is usually mixed with gum or starch, and applied by means of blocks or wooden engravings in relief, or from copper plates, and the colours are brought out by immersion in vessels filled with suitable compositions. Dyers call the latter fluid the bath. The art of printing affords many processes, in which the effect of mordants, both simple and compound, is exhibited. The following is taken from Berthollet.

The mordant employed for linens, intended to receive different shades of red, is prepared by dissolving in eight pounds of hot water, three pounds of alum, and one pound of acetate of lead, to which two ounces of potash, and afterward two ounces of powdered chalk, are added.

In this mixture the sulphuric acid combines with the lead of the acetate and falls down, because insoluble, while the argillaceous earth of the alum unites with the acetic acid disengaged from the acetate of lead. The mordant therefore consists of of an argillaceous acetic salt, and the small quantities of alkali and chalk serve to neutralize any disengaged acid, which might be contained in the liquid.

Several advantages are obtained by thus changing the acid of the alum. First, the argillaceous earth is more easily disengaged from the acetic acid, in the subsequent processes, than it would have been from the sulphuric. Secondly, this weak acid does less harm when it comes to be disengaged by depriving it of its earth. And thirdly, the acetate of alumina not being crystallizable like the sulphate, does not separate or curdle by drying on the face of the blocks for printing, when it is mixed with gum or starch.

When the design has been impressed by transferring the mordant from the face of the wooden blocks to the cloth, it is then put into a bath of madder, with proper attention, that the whole shall be equally exposed to this fluid. Here the piece be

46

1

DYE

comes of a red colour, but deeper in those places where the mordant was applied. →For some of the argillaceous earth had before quitted the acetic acid, to combine with the cloth; and this serves as an intermedium to fix the colouring matter of the madder, in the same manner as the acid of galls, in the former instance, fixed the particles of oxide of iron. With the piece in this state, the calico-printer has only therefore to avail himself of the difference between a fixed and a fugitive colour. He therefore boils the piece with bran, and spreads it on the grass. The fecula of the bran takes up part of the colour, and the action of the sun and air renders more of it combinable with the same substance.

In other cases, the elective attraction of the stuff to be dyed has a more marked agency. A very common mordant for woollens is made by dissolving alum and tartar together; neither of which is decomposed, but may be recovered by crystallization upon evaporating the liquor. Wool is found to be capable of decomposing a solution of alum, and combining with its earth; but it seems as if the presence of disengaged sulphuric acid served to injure the wool, which is rendered harsh by this method of treatment, though cottons and linens are not, which have less attraction for the earth. Wool-also decomposes the alum, in a mixture of alum and tartar; but in this case there can be no disengagement of sulphuric acid, as it is immediately neutralized by the alkali of the tartar.

Metallic oxides have so great an attrac. tion for many colouring substances, that they quit the acids in which they were dis

solved, and are precipitated in combination

with them. These oxides are also found by experiment to be strongly disposed to combine with animal substances; whence in many instances they serve as mordants,

or the medium of union between the colouring particles and animal bodies.

The colours which the compounds of metallic oxides and colouring particles assume, then, are the product of the colour peculiar to the colouring particles, and of that peculiar to the metallic oxide.

* The following are the dye-stuffs used by the calico-printers for producing fast colours. The mordants are thickened with gum, or calcined starch, and applied with the block, roller, plates, or pencil.

1. Black. The cloth is impregnated with acetate of iron (iron liquor), and dyed in a bath of madder and logwood.

2. Purple. The preceding receding mordant of iron, diluted; with the same dyeing bath. 3 Crimson. The mordant for purple, united with a portion of acetate of alumina, or red mordant, and the above bath. 4. Red. Acetate of alumina is the mor

DYE

dant, (see ALUMINA), and madder is the dye-stuff.

5. Pale red of different shades. The preceding mordant diluted with water, and a weak madder bath.

6. Brown or Pompadour. A mixed mordant, containing a somewhat larger proportion of the red than of the black; and the dye of madder.

7. Orange. The red mordant; and a bath first of madder, and then of quercitron.

8. Yellow. A strong red mordant; and the quercitron bath, whose temperature should be considerably under the boiling point of water.

9. Blue. Indigo, rendered soluble and greenish-yellow coloured, by potash and orpiment. It recovers its blue colour, by exposure to air, and thereby also fixes firmly on the cloth. An indigo vat is also made, with that blue substance, diffused in water with quicklime and copperas. These substances are supposed to deoxidize indigo, and at the same time to render it soluble. Golden-dye. The cloth is immersed alternately in a solution of copperas and limewater. The protoxide of iron precipitated on the fibre, soon passes by absorption of atmospherical oxygen, into the golden-coloured deutoxide.

Buf. The preceding substances, in a more dilute state.

Blue vat, in which white spots are left on a blue ground of cloth, is made, by applying to these points a paste composed of a solution of sulphate of copper and pipeclay; and after they are dried, immersing it

stretched on frames for a definite number of minutes, in the yellowish-green vat, of 1 part of indigo, 2 of copperas, and 2 of lime,

with water.

Green. Cloth dyed blue, and well washed, is imbued with the aluminous acetate, dried, and subjected to the quercitron bath.

In the above cases, the cloth, after receiving the mordant paste, is dried, and put through a mixture of cow dung and warm water. It is then put into the dyeing vat or copper.

Fugitive Colours.

All the above colours are given, by making decoctions of the different colouring woods; and receive the slight degree of fixity they possess, as well as great brilliancy, in consequence of their combination or admixture with the nitro-muriate of tin.

1. Red is frequently made from Brazil and Peachwood.

2. Black. A strong extract of galls, and deuto-nitrate of iron.

3. Purple. Extract of logwood and the deuto-nitrate.

4. Yellow. Extract of quercitron bark, or French berries, and the tin solution. 5. Blue. Prussian blue and solution of tin.

MJ