* DIALLAGE. A species of the genus Schiller spar. Diallage has a grass-green colour. It occurs massave or disseminated. Lustre glistening and pearly. Cleavage imperfect double. Translucent. Harder than fluor spar. Brittle. Sp.gr.3.1. It melts before the blow-pipe into a gray or greenish enamel. Its constituents are 50 silica, 11 alumina, 6 magnesia, 13 lime, 5.3 oxide of iron, 1.5 oxide of copper, 7.5 oxide of chrome.Vauquelin It occurs in the island of Corsica, and in Mont Rosa in Switzerland, along with saussurite. It is the verde di Corsica duro of artists, by whom it is fashioned into ring-stones and snuff-boxes. It is the smaragdite of Saussure. The diallage in the rock is called gabbro. * DIAMOND. Colours white and gray, also red, brown, yellow, green, blue, and black. The two last are rare. When cut it exhibits a beautiful play of colours in the sunbeam. It occurs in rolled pieces, and also crystallized: 1st, In the octohedron, in which each plane is inclined to the adjacent, at an angle of 109° 28′ 16". The faces are usually curvahnear. This is the fundamental figure.2d, A simple three-sided pyramid, truncated on all the angles. 3d, A segment of the octohedron. 4th, Twin crystal. 5th, Octohedron, with all the edges truncated. 6th, Octohedron, flatly bevelled on all the edges. 7th, Rhomboidal dodecahedron. 8th, Octohedron with convex faces, in which each is divided into three triangular ones, forming altogether 24 faces. 9th, Octohedron, in which each convex face is divided into six planes, forming 48 in all. 10th, Rhomboidal dodecahedron, with diagonally broken planes. 11th, A flat double three-sided pyramid. 12th, Very flat double three-sided pyramid, with cylindrical convex faces. 13th, Very flat double six-sided pyramid. 14th, Cube truncated on the edges. Crystal small. Surface rough, uneven, or streaked. Lustre splendent, and internally perfect adamantine. Cleavage octohedral, or parallel to the sides of an octohedron. Foliated structure. Fragments octohedral or tetrahedral. Semi-transparent. Refracts single. Scratches all known minerals. Rather easily frangible. Streak gray. Sp. gr. 3.4 to 3.6. It consists of pure carbon, as we shall presently demonstrate. When rubbed, whether in the rough or polished state, it shows positive electricity; whereas rough quartz affords negative. It becomes phosphorescent on exposure to the sun, or the electric spark, and shines with a fiery light. In its power of refracting light it is exceeded only by red lead-ore, and or piment. It reflects all the light falling on its posterior surface at an angle of incidence greater than 24° 13', whence its great lustre is derived. Artificial gems reflect the half of this light. It occurs in imbedded grains and crystals in a sandstone in Brazil, which rests on chlorite and clay-slate. In India the diamond bed of clay is underneath beds of red or bluish-black clay; and also in alluvial tracts both in India and Brazil. For the mode of working diamond mines, and cutting and polishing diamonds, consult Jameson's Mineralogy, vol. i. p. 11. The diamond is the most valued of all minerals. Dr. Wollaston has explained the cutting principle of glaziers' diamonds, with his accustomed sagacity, in the Phil. Trans. for 1816. The weight, and consequently the value of diamonds, is estimated in carats, one of which is equal to four grains, and the price of one diamond, compared to that of another of equal colour, transparency, purity, form, &c. is as the squares of the respective weights. The average price of rough diamonds that are worth working, is about L. 2 for the first carat. The value of a cut diamond being equal to that of a rough diamond of double weight, exclusive of the price of workmanship, the cost of a wrought diamond of 100 do. is 1002 X L.8, = 80000. This rule, however, is not extended to diamonds of more than 20 carats. The larger ones are disposed of at prices prices inferior to their value by that computation. The snowwhite diamond is most highly prized by the jeweller. If transparent and pure, it is said to be of the first water. The carat grain is different from the Troy grain. 156 carats make up the weight of one oz. troy; or 612 diamond grains are contained in the Troy ounce. From the high refractive power of the diamond, MM. Biot and Arago supposed that it might contain hydrogen. Sır H. Davy, from the action of potassium on it, and its non-conduction of electricity, suggested in his third Bakerian lecture that a minute portion of oxygen might exist in it; and in his new experiments on the fluoric compounds, he threw out the idea, that it might be the carbonaceous principle, combined with some new, light, and subtle element, of the oxygenous and chlorine class. This unrivalled chemist, during his residence at Florence in March 1814, made several experiments on the combustion of the diamond and of plumbago by means of the great lens in the cabinet of natural history, the same instrument as that employed in the first trials on the action of the solar heat on the diamond, instituted in 1694 by Cosmo III. Grand Duke of Tuscany. He subsequently made a series of researches on the combustion of different kinds of char. coal at Rome. His mode of investigation was peculiarly elegant, and led to the most decisive results. He found that diamond, when strongly ignited by the lens, in a thin capsule of platinum, perforated with many orifices, so as to admit a free circulation of air, continued to burn with a steady brilliant red light, visible in the brightest sunshine, after it was with drawn from the focus. Some time after the diamonds were removed out of the focus, indeed, a wire of platina that attached them to the tray was fused, though their weight was only 1.84 grains. His apparatus consisted of clear glass globes of the capacity capacit of from 14 to 40 cubic inches, having single apertures to which stop-cocks were attached. A small hollow cylinder of platinum was at tached to one end of the stop-cock, and was mounted with the little perforated capsule for containing the diamond. When the experiment was to be made, the globe containing the capsule and the substance to be burned was exhausted by an excellent air pump, and pure oxygen, from chlorate of potash, was then introduced. The change of volume in the gas after combustion was estimated by means of a fine tube connected with a stop-cock, adapted by a proper screw to the stop-cock of the globe, and the absorption was judged of by the quantity of mercury that entered the tube, which afforded a measure so exact, that no alteration however minute could be overlooked. He had previously satisfied himself that a quantity of moisture, less than 1-100th of a grain, is rendered evident by deposition on a polished surface of glass; for a piece of paper weighing one grain was introduced into a tube of about four cubic inches capacity, whose exterior was slightly heated by a candle. A dew was immediately perceptible on the inside of the glass, though the paper, when weighed in a balance turning with 1-100th of a grain, indicated no appreciable diminution. The diamonds were always heated to redness before they were introduced into the capsule. During their combustion, the glass globe was kept cool by the application of water to that part of it immediately above the capsule, and where the heat was great est. From the results of his different experiments, conducted with the most unexceptionable precision, it is demonstrated, that diamond affords no other substance by its combustion than pure carbonic acid gas; and that the process is merely a solution of diamond in oxygen, without any change in the volume of the gas. It likewise appears, that in the combustion of the different kinds of charcoal, water is produced; and that from the diminution of the volume of the oxygen, there is every reason to believe that the water is formed by the combustion of hydrogen existing in strongly ignited charcoal. As the charcoal from oil of turpentine left no residuum, no other cause but the presence of hydrogen can be assigned for the diminution occasioned in the volume of the gas during its combustion. The only chemical difference perceptible between diamond and the purest charcoal is, that the last contains a minute portion of hydrogen; but can a quantity of an element, less in some cases than 1-50,000th part of the weight of the substance, occasion so great a difference in physical and chemical characters? The opinion of Mr. Tennant, that the difference depends on crystallization, seerns to be correct. Transparent solid bodies are in general non-conductors of electricity; and it is probable that the same corpuscular arrangements which give to matter the power of transmitting and polarizing light, are likewise connected with its relations to electricity. Thus water, the hydrates of the alkalis, and a number of other bodies which are conductors of electricity when fluid, become non-conductors in their crystallized form. That charcoal is more inflammable than the diamond, may be explained from the looseness of its texture, and from the hydrogen it contains. But the diamond appears to burn in oxygen with as much facility as plumbago, so that at least one distinction supposed to exist between the diamond and common carbonaceous substances is done away by these researches. The power possessed by certain carbonaceous substances of absorbing gases, and separating colouring matters from fluids, is probably mechanical, and dependent on their porous organic structure; for it belongs in the highest degree to vegetable and animal charcoal, and it does not exist in plumbago, coak, or anthracite. The nature of the chemical difference between the diamond and other carbonaceous substances, may be demonstrated by igniting them in chlorine, when muriatic acid is produced from the latter, but not the former.The visible acid vapour is owing to the moisture present in the chlorine uniting to the dry muriatic gas. But charcoal, after being intensely ignited in chlorine, is not altered in its conducting power or colour This circumstance is in favour of the opinion, that the minute quantity of hydrogen is not the cause of the great difference between the physical properties of the diamond and charcoal.* It does not appear that any sum exceeding one hundred and fifty thousand pounds has been given for a diamond. *DICHROITE. See IOLITE.* DIGESTION. The slow action of a solvent upon any substance. * DIGESTION. The conversion of food into chyme in the stomach of animals by the solvent power of the gastric juice. Some interesting researches have been lately made on this subject by Dr. Wilson Philip and Dr. Prout. Phenomena, &c. of digestion in a rabbit.A rabbit which had been kept without food for twelve hours, was fed upon a mixture of bran and oats. About two hours afterwards it was killed, and examined immediately while still warm, when the following circumstances were noticed: The stomach was moderately distended, with a pulpy mass, which consisted of the food in a minute state of division, and so intimately mixed, that the different articles of which it was composed could be barely recognized. The digestive process, however, did not appear to have taken place equally throughout the mass, but seemed to be confined principally to the superficies, or where it was in contact with the and that next in turn succeeds to undergo the same change. Thus a continual motion is going on; that part of the food which lies next the surface of the stomach passing towards the pylorus, and the more central parts approaching the surface." Dr. Philip has remarked, that the great end of the stomach is the part most usually found acted upon by the digestive fluids after death. The following phenomena were observed by Dr. Prout: Comparative examination of the contents of the duodena of two dogs, one of which had been fed on vegetable food, the other on animal food only. The chymous mass from vegetable food (principally bread) was composed of a semi-fluid, opaque, yellowish-white part, containing another portion of a similar colour, but firmer consistence, mixed with it. Its specific gravity was 1.056. It showed no traces of a free acid, or alkali; but coagugentle heat. stomach. The smell of this mass was peculated milk completely, when assisted by a fiar, and difficult to be described. It might be denominated fatuous and disagreeable. On being wrapped up in a piece of linen, and subjected to moderate pressure, it yield ed upwards of half a fluid ounce of an opaque reddish-brown fluid, which instantly reddened litmus paper very strongly. It instantly coagulated milk, and, moreover, seemed to possess the property of redissolving the curd and converting it into a fluid, very similar to itself in appearance. It was not coagulated by heat or acids; and, in short, did not exhibit any evidence of an albuminous principle. On being evaporated to dryness, and burned, it yielded very copious traces of an alkaline muriate, with slight traces of an alkaline phosphate and sulphate; also of various earthy salts, as the sulpha te phosphate, and carbonate of lime. "The first thing," says Dr. P. “which strikes the eye on inspecting the stomachs of rabbits which have lately eaten, is, that the new is never mixed with the old food. The former is always found in the centre surrounded on all sides by the old food, except that on the upper part between the new food and the smaller curvature of the stomach, there is sometimes little or no old food. If the old and the new food are of different kinds, and the animal be killed after taking the latter, unless a great length of time has elapsed after taking it, the line of separation is perfectly evident, so that the old may be removed without disturbing the new food. "It appears that in proportion as the food is digested, it is moved along the great curvature, when the change in it is rendered more perfect, to the pyloric portion. The layer of food lying next the surface of the stomach, is first digested. In proportion as this undergoes the proper change, it is moved on by the muscular action of the stomach, That from animal food was more thick and viscid than that from vegetable food, and its colour was more inclined to red. Its sp. gr. was 1.022. It showed no traces of a free acid or alkali; nor did it coagulate milk even when assisted by the most favourable circumstances. On being subjected to analysis, these two specimens were found to consist of traces of this principle could be perceived See SANGUIFICATION.* DIGESTIVE SALT. Muriate of potash. DIGESTER. The digester is an instrument invented by Mr. Papin about the beginning of the last century. It is a strong vessel of copper or iron, with a cover adapted to screw on with pieces of felt or paper interposed. A valve with a small aperture is made in the cover, the stopper of which valve may be more or less loaded either by actual weights, or by pressure from an apparatus on the principle of the steelyard. The purpose of this vessel is to prevent the loss of heat by evaporation. The solvent power of water when heated in this vessel is greatly increased. * DIOPSIDE. A sub-species of oblique edged augite. Its colour is greenish-white. It occurs massive, disseminated, and crystallized: 1. In low oblique four-sided prisms. 2. The same, truncated on the acute lateral edges, bevelled on the obtuse edges, and the edge of the bevelment truncated. 3. Eight-sided prisms. The broader lateral planes are deeply longitudinally streaked, the others are smooth. Lustre shining and pearly. Fracture uneven. Translucent.As hard as augite. Sp. gr. 3.3 It melts with difficulty before the blow-pipe. It consists of 57.5. silica, 18.25 magnesia 16.5 lime, 6 iron and manganese. Laugier. It is found in the hill Ciarmetta in Piedmont; also in the black rock at Mussa, near the town of Ala, in veins along with epidote or pistacite, and hyacinth-red garnets. It is the Alalite and Mussite of Bonvoisin.* * DIOPTASE. Emerald copper-ore." * DIPPEL'S animal oil, an oily matter obtained in the igneous decomposition of horns in a retort. Rectified, it becomes colourless, aromatic, and as light and volatile as ether. It changes sirup of violets to a green from its holding a little ammonia in solution.* * DIPYRE. Schmelszstein. This mineral is distinguished by two characters; it is fusible with intumescence by the blow-pipe, and it emits on coals a faint phosphorescence. It is found in small prisms united in bundles, of a grayish or reddishwhite. These crystals are splendent, hard enough to scratch glass; their longitudinal fracture is lamellar, and their cross fracture conchoidal. Its sp. gr. is 2.63. The primi tive form appears to be the regular six-sided prism. It consists of 60 silica, 24 alumina, 10 lime, 2 water, and 4 loss.-Vauquelin. It occurs in a white or reddish steatite, mingled with sulphuret of iron, on the right bank of the torrent of Mauléon in the western Py renees.* * DISTILLATION. The vaporization and subsequent condensation of a liquid, by means of an alembic, or still and refrigeratory, or of a retort and a receiver. The old distinctions of distillatio per latus, per ascensum, and per decensum, are now discarded. Under LABORATORY, a drawing and description of a large still of an ingenious construction is given. The late celebrated Mr. Watt having ascertained, that liquids boiled in vacuo at much lower temperatures than under the pressure of the atmosphere, applied this fact to distillation; but he seems, according to Dr. Black's report of the experiment, to have found no economy of fuel in this elegant process; for the latent heat of the vapour raised in vacuo, appeared to be considerably greater than that raised in ordinary circumstances. Mr. Henry Tritton has lately contrived a very simple apparatus for performing this operation in vacuo; and though no saving of fuel should be made, yet superior flavour may be secured to the distilled spirits and essential oils, in consequence of the moderation of the heat. The still is of the common form; but instead of being placed immediately over a fire, it is immersed in a vessel containing hot water. The pipe from the capital bends down and terminates in a cylinder or barrel of metal plunged in a cistern of cold liquid. From the bottom of this barrel, a pipe proceeds to another of somewhat larger dimensions, which is surrounded with cold water, and furnished at its top with an exhausting syringe. will The pipe from the bottom of the still, for emptying it, and that from the bottom of each barrel, are provided with stop-cocks. Hence, on exhausting the air, the liquid w distil rapidly, when the body of the alembic is surrounded with boiling water. When it is wished to withdraw a portion of the distilled liquor, the stop-cock at the bottom of the first receiver is shut, so that on opening that at the second, in order to empty it, the vacuum is maintained in the still. It is evident that the first receiver may be surrounded with a portion of the liquid to be distilled, as I have already explained in treating of alcohol. By this means the utmost economy of fuel may be observed. The term distillation, is often applied in this country, to the whole process of converting malt or other saccharine matter, into spirits or alcohol. In making malt whiskey, one part of bruised malt, with from four to nine parts of barley meal, and a proportion of seeds of oats, corresponding to that of the raw grain, is infused in a mash-tun of cast iron, with from 12 to 13 wine gallons of water, at 150° Fahr. for every bushel of the mixed farinaceous matter. The agitation then given by manual labour or machinery to break down and equally diffuse the lumps of meal, constitutes the process of mashing. This operation continues two hours or upwards, according to the proportion of ummalted barley, of during which the temperature is kept up, by the effusion of seven or eight additional gallons of water, a few degrees under the boiling temperature. The infusion termed wort having become progressively sweeter, is allowed to settle for two hours, and is run off from the top, to the amount of about onethird the bulk of water employed. About eight gallons more of water, a little under 200° F. are now admitted to the residuum, infused for nearly half an hour with agitation, and then left to subside for an hour and a half, when it is drawn off. Sometimes a third affusion of boiling water, equal to the first quantity, is made, and this infusion is generally reserved to be poured on new farina; or it is concentrated by boiling and added to the former liquors. In Scotland, the distiller is supposed by law, to extract per cent 14 gallons of spirits, sp. gr. 0.91917, or 1 to 10 over proof, and must pay duty accordingly. Hence, his wort must have at least the strength of 55 pounds saccharine matter, per barrel, previous to letting it down into the fermenting tun; and the law does not permit it to be stronger than 75 pounds. Every gallon of the above spirits contains 4.6 pounds of alcohol, sp. gr. 0.825, and requires for its production the complete decomposition of twice 4.6 pounds of sugar = 9.2 pounds. But since we can never count on decomposing above fourfifths of the saccharine matter of wort, we must add one-fifth to 9.2 pounds, when we shall have 11 pounds for the weight of saccharine matter, equivalent in practice to one gallon of the legal spirits. Hence, the distiller is compelled to raise the strength of his wort up to nearly 70 pounds per barrel as indicated by his saccharometer. This concentration is to be regretted, as it materially injures the flavour of the spirit. The thinner worts of the Dutch, give a decided superiority to their alcohols. At 62 pounds per barrel, we should have about 12 per cent of spirits of the legal standard. To prevent acetification, it is necessary to cool the worts down to the proper fermenting temperature of 70°, or 65°, as rapidly as possible. Hence, they are pumped immediately from the mash-tun into extensive wooden troughs, two or three inches deep, exposed in open sheds to the cool air; or they are made to traverse the convolutions of a pipe, immersed in cold water.The wort being now run into the fermenting tun, yeast is introduced and added in nearly equal successive portions, during three days; amounting in all to about one gallon, for every two bushels of farinaceous matter. The temperature rises in three or four days, to its maximum of 80°; and at the end of 10 or 12 days the fermentation is completed; the tuns being closed up during the last half of the period. The distillers do not collect the yeast from their fermenting tuns, but allow it to fall down, on the supposition that it enhances the quantity of alcohol. The specific gravity of the liquid has now probably sunk from 1.060, that of wort equivalent to about 56 pounds per barrel, to 1.005, or 1.000; and consists of alcohol mixed with undecomposed saccharine and farinaceous matter. The larger the proportion of alcohol, the more sugar will be preserved unchanged; and hence the impolicy of the present laws on distillation. Some years ago, when the manufacturer paid a duty for the season, merely according to the measurement of his still, it was his interest to work it off with the utmost possible speed. Hence the form of still and furnace described under LABORATORY, was contrived by some ingenious Scotch distillers, by which means they could work off in less than four minutes, and recharge, an 80 gallon still; an operation which had a few years before lasted several days, and which the vigilant framers of the law, after recent investigation, deemed possible only in eight minutes. The waste of fuel was however great. The duties being now levied on the product of spirit, the above contest against time no longer exists. It has been supposed, but I think grounds, that quick distillation injures the flavour of spirits. This I believe to depend, almost entirely, on the mode of conducting the previous fermentation. on insufficient In distilling off the spirit from the fermented wort or wash, a hydrometer is used to ascertain its progressive diminution of strength, and when it acquires a certain weakness, the process is stopped by opening the stopcock of the pipe, which issues from the bottom of the still, and the spent wash is removed. There is generally introduced into the still, a bit of soap, whose oily principle spreading on the surface of the boiling liquor, breaks the large bubbles, and of course checks the tendency to froth up. The spirits of the first distillation, called in Scotland low wines, are about 0.975 sp. gravity, and contain nearly 20 per cent of alcohol of 0.825. Redistillation of the low wines, or doubling, gives at first the fiery spirit called first-shot, milky and crude, from the presence of a little oil. This portion is returned into the low wines, What flows next is clear spirit, and is received in one vessel, till its density diminish to a certain degree. The remaining spirituous liquor, called faints, is mixed with low wines, and subjected to another distillation. The manufacturer is hindered by law from sending out of his distillery, stronger spirits than 1 to 10 over hydrometer proof, equivalent to sp. gr. 0.90917; or weaker spirits than 1 in 6 under proof, whose sp. gr. is 0.9385. |