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With ammonia forms a soapy emulsion. Nitric acid heated on it dissolves and converts it into oxalic acid. It resembles refined bees'wax, and serves for making candles. The fibrous substance is procured by decanting the melted ■waxy matter, washing off the last portion of it with an essential oil, squeezing the residuum, and boiling it a long time in water, to volatilize the oil, the odour of which cannot, however, be completely discharged. Thus obtained, the fibrous matter is brown, having been somewhat altered by the temperature of the melted wax. It is tasteless. Placed on a hot iron, it twists itself and swells up, melts, and is carbonized, diffusing the smell of broiled meat. Alcohol does not dissolve it; and hence, by treating the extract of the vegetable milk repeatedly with hot alcohol, the fibrous matter is obtained white and flexible. In this state it dissolves readily in diluted muriatic acid. It possesses the same properties, therefore, as animal flbrine. Fibrine had already been found in the milky juice of the carica papaya, by Vauquelin. Besides these two main constituents, the vegetable milk contains a little sugar, a magnesian salt (not an acetate), and water. It contains neither caseum nor caoutchouc. By incineration some silica, lime, phosphate of lime, and magnesia were obtained. The wax forms about one half the weight of the milk.—Annales (it Physique tt Je Chemie.

ATMOSPHERE OF SEAS.

M. Vogel, of Munich, after a number of researches, from which, judging by his name, (Bird) we should suppose him extremely well qualified, states, that—1st, the air of the channel between Dieppe and Havre contains muriates; 2dly, the air of the Channel, as well as; the air of the Baltic, contains less carbonic acid than the air of the Continent; 3dly; the mariates do not disengage their acid at a temperature capable! of bringing them to ebullition, but they are partly

volatilised with the vapours of the water; 4thly, there is no particular colouring principle in sea air, as has been supposed,; 5thly, all waters containing muriates acquire a wine red colour, with nitrat of silver, when exposed to the sun.

FIELD MICE. In 1809 or 1810, in the monjh of August, there appeared such quantities of field mice in Morvern, that the inhabitants discovered these were more mischievous enemies than tax-gatherers or excisemen. They disappeared, however, during the ensuing winter, leaving the good people with an opinion, that it was better to have them for a few months than a few years. Every spot of fine pasture in the neighbourhood was cut into roads; the grass, bit through at the roots, lay withered on the ground; bushes, also, nibbled at the roots, decayed and died. The bark of young wood was knawed off, and the ground undermined to such a degree by their subterraneous residences, that it often yielded to the foot in walking. These subterraneous residences were intended for winter quarters; and it was observed th« nests all communicated with each other by means of cross roads, and every nest had a connexion by one of these roads, with some placewhere there was water. At one farm in Morvern the crop was completely destroyed; every square foot of the roi>f'o{the barn was per-. , forated, and the rods fastening the thatch bit through. The subsequent winter was very severe, and it is supposed they perished for want of food. These little animals did an immense deal of injury, destroying the young fir-trees, by eating away the bark a little abovet the root. So ruinous were they to the plantations, that an army of women and cats were stationed, night and day, so as to cover the whole domains of a Colonel Maolean from the incursions of thisenejnjjr. It would appear,, howjever, thpt this force was insufficient; and, in spite of these sentinels, the Colonel's property-wirS'much ravaged.

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BLEACHING.

Art. IV.

CONCLUSION.

Our papers on this subject have been hitherto confined to the more general practices of bleaching linen; in the present paper, the last on the subject, we mean shortly to advert to the bleaching of silk and wool, to bleaching muslin, and to that great branch of our domestic manufacture, bleaching cotton for calico printing. First, however, we have to give a little tabular view of linen bleaching, in which the quantity of linen bleached, and the quantity of materials employed, are precisely stated.

A parcel of goods, to which this table refers, consists of 360 pieces of what are called Britannias, each thirty-five yards long, and weighing on an average lOlbs., so that the weight of the whole is 3600lbs. After the first washing and fermentation, they are submitted to the following process:—

1. Backed, wilh fiOlbs. of pearl-ashes, washed and exposed on the held.

2. Ditto, with BUlbii. do. again washed, and exposed.

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3. Ditto, OOlbs. potashes, washed, and exposed.

4. Ditto, 80 do..

5. Ditto, HO do..

6. Ditto, 50 do..

7. Ditto, 70 do..

8. Ditto, 70 do..

9. Soured one night in dilute sulphuric acid.

10. Bucked, with 501bs. of pearl-ashes, washed, and exposed.

11. -Immersed in oxymuriate of potash for 12 hours.

12. Boiled, with .IOlbs. of pearl-ashes, washed, and exposed.

13. Ditto do do do.;

11. Soured and washed.

By this process, 690 pounds weight of alkali is taken to bleach 360 pieces of linen; so that somewhat less than tws pounds of alkali is employed for each piece. Some, however, of the pieces ar» found not to be fully bleached by this; and, therefore, two pounds may be stated as the average of alkali employed to bleach one piece of linen. The bleaching power of these substances depends on the quantity of pure alkali they contain; and this quantity, or their strength, is judged of by the quantity of an acid it takes to saturate them. The substances sold in commerce, under the names of potashes, pearl-ashes,

<bij»<i oi8 tsdliwd .uotfilliMfo oJ

&c. are not, as is well known, pure It is then infused a second time in

alkali; it is, therefore, of great con- the same mixture, for four or six

sequence to the practical bleacher, days, and is then again washed as>

to know which substance contains before. By this process silk may

the most alkali. The following, be made to surpass in whiteness

which is the result of numerous and lustre, says M. Baum6, the

experiments, is given as the quan- finest specimens from Nankin; bat

tity of pure alkali contained in one the ordinary method is different

hundred parts of the different from that recommended by this

alkaline substances met with in gentleman, and is as follows:—The

commence and employed by the raw silk is put into a bag of thin

bleacher:— linen, and thrown into a vessel of

Best American pearl-ashes. 60 to ?3 boiling river water, in which good

Caustic do. potash in reddish Toulon or Genoa, soap has been

lumps.... 60 — 63 dissolved. After boiling two or

lecondt^-LheT 50=55 three hours> the ba* being fre'

White Russ^u pearl-ashes'.'.'.'.'i>2- 58 fluently turned, it is taken out,

White Dantzicdo 45 — 52 beaten, and washed in cold water..

Alicant barilla 20 —,33 It is then wrung slightly,and again

Inferior kinds of barilla.... 10—15 put into a copper with cold water,

Natron 20 — 32 miXed with soap and a little in

The quantity of sulphuric acid digo, whence it derives the bluish

employed in making the sour- tint generally observed in it. It is

ings, varies in different bleaching- afterwards wrung hard with a

grounds. In Ireland the propor- woodeu stake, and then shook to

tion of sulphuric acid to water, by separate the threads from one an

xaeasure, is stated to be as 1 to other. It is then suspended in a

640; while in Lancashire the pro- stove or chamber, constructed for

portion is as high as 1 to 46, or the purpose, and sulphur is burnt

by weight, one pound of sulphuric under it, the vapour of which gives

acid to 25 pounds of water, the the last degree of whiteness kto the

sulphuric acid being twice the silk.

weight of water. In some parts of Woollen Stuffs are thus Scotland the bleachers for calico bleached :—After coming out_ of printing employ even one measure the fuller's mill, they are put into of sulphuric acid to 25 measures soap and water, warm, in which of water; and it is sufficient to im- they are again worked by the merse the cotton five or six hours in strength of the arms over a wooden this souring. No certain data can bench; and by this means they be given as to the strength of the acquire that whiteness which the oxyrauriatic solutions, as they vary fuller's mill had begun to give very much. The manufacture of them. When sufficiently worked sulphuric acid being conducted on by the hand, they are washed in a large scale for numerous other clear water and dried. This is callpurposes, as well as bleaching, we ed the natural method. Or the stuffs we shall hereafter give a descrip- are thoroughly washed in river tion of this. water, and when half dry they are

The Best Method Of Bleach- stretched out in a close stove in Ikg Silk,according toM. Baume.is which sulphur is burnt, the vapour this: on six pounds of yellow raw of which diffuses itself over the silk, placed in an earthen vessel, whole stuff, adhering to it and pour 48 pounds of alcohol, of the giving it a fine whiteness. This is specific gravity 0.867, mixed with called Bleaching by the Flower, or 12 ounces of muriatic acid, of the Bleaching of Paris, because they specific gravity 1.100. The silk use this method more in that cityremains in the liquid, which passes than any where else. from fine green to a dusky brown, Muslins Are Thus Bleached. one day, and is then taken out, The coarser kinds, after they have drained, and washed with alcohol, been steeped and washed, are first

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this process is repeated till the cloth is of a proper whiteness; after which it is soured and washed, as in the ordinary method. Oxymuriaticacid may be employed at proper intervals. Nine steeps, with exposure to steam, is found sufficient for linen, and five for cotton. By this method a considerable quantity of alkali is saved, as none of that which is employed is wasted.

In Bleaching Calicoes for the printer, a pure white is not so much the object to be attained, as that the colouring matter and the vegetable oil are fully extracted, or the cloth is what is called well rooted. This is effected by boiling and bucking the cloth, if linen, nine or ten times, and if cotton, five or six times, in a solution of alkali, rendered caustic by quick lime. The alkaline solution must be well settled, and transparent as water; because, if the lime remains either suspended or irrsolution in the water, it is apt to be deposited in the clotb, and destroy the purity of the parts intended to be white. To ascertain if the cloth be ready for printing, a strip is torn from the end, and printed with one of the mordants used to fix the dye. The cloth is then rinsed and immersed in cold water, which contains madder; the heat is gradually increased, and the cloth is alternately lifted up and down in the madder solution, till the colour is dyed of the required shade. If the cloth be properly bleached, the place stained with the mordant will alone have attracted the colouring matter of the madder, and the rest of the piece will remain white. If not properly bleached, the part intended for white will be stained a dirty light red, and it must again be boiled in the solution" of alkali.

In bleaching either linen or cotton for printing, it is not customary to immerse them in any oxymuriatic solution, except in winter, when it is difficult to obtain a good, white. When exposed also on the green, they are not artificially watered, but are merely exposed tothe vicissitudes of the weather; and hence this method is called dry bleaching.

We now come to the most peculiar part of this branch of bleaching; which is, restoring the white without injuring the colours after the printing is completed. When this is done, the white is generally very dull, owing partly to the imperfect manner in which the cloth has been bleached, partly to the mordant having been loosened by the increased temperature of the water, which uniting with the madder, or other colouring matter, is spread over the parts intended to be white. To remove this dulness "without much exposure on the bleaching-green was long a desideratum; it is now effected by means of oxymuriate of magnesia. The usual methods of bleaching, and the application of oxymuriate, either of lime or of potash, either changed the colours or rendered them duller, or wholly discharged them. Oxymuriate of magnesia has neither of these effects it clears the white without injuring or alteringthecolours. Ithas beenfound by experience, that of all the alkaline earths which are partially soluble in water, magnesia has the least effect in changing colours, which makes it well adapted, when mixed •with the chlorine or oxymuriate, to the purpose of clearing the stains from the white of printed goods.

Our plate represents the apparatus now most generally employed to make the oxymuriate of magnesia. A is a furnace; B a cast iron vessel, to serve as a water-bath for the reception of C, a still made of lead, and adapted to the cast iron waterbath,' in which it stands; dd are water lutes for the still to drop into, •which keeps the whole tight and prevents the escape of gas; E is the head of the still, which dips into the gutter of water surrounding the still, and enables the workmen to take it off and put it on without difficulty ; fff are pipes and tubes; CC is a stirrer, made of a square piece of wood covered with lead; H a bent fun

nel for pouring in the acid; I an intermediate vessel to arrest any uncombined acid which arises during the process; K is a receiver made of lead, into which the alkaline solution is put, and which, when saturated, may be drawn off at N; L is the opening; and M IVt the stirrer, which, in large works, is moVed by being connected with a steam-engine, or some other power. In preparing the magnesian solution, the earth must be broken ia water like starch; it is then introduced into the receiver, K. Into the still, C, is put one part of good manganese, on which is poured two parts of muriatic acid diluted with its bulk of water; oxymuriati© acid is separated, passes ir.to'K, and dissolves the magnesia.which is kept suspended in the water by constant stirring. When it is required for use, as large a portion of it is drawn off into a copper containing water, and heated to the temperature of 170° of Fahrenheit, as will give the water a perceptible taste; and as soon as it is drawn off, the two must be mixed together by means of a clean broom. Tho printed goods are then run over the wince into the copper, till the white* is sufficiently clear, which requires only a few, minutes, and immediately afterwards the goods are streamed in pure water to prevent the further action of tk<? bleaching fluid.

CHEMISTRY AS A SCIENCE. Art. VI.

HYDROGEN.

Hydrogen gas, the substance we are now to describe, for nothing is known of its base to which the term hydrogen strictly applies,'is so named from a Greek word, signifying water-former. Hydrogen, in combination with oxygen, forming that fluid, and being always procured from it. By chemists it is considered as the distinguishing constituent element of water, which has now, for some time, been classed among compound substances.

The gas is thus procured :—put into the retort A, described in No. IV, Fig. 2, a quantity of iron filings.

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