Crystals Sentence Examples

Crystals of azurite belong to the monoclinic system; they have a vitreous lustre and are translucent.

The crystals of prismatic habit represented in figs.

It forms monoclinic crystals which are very soluble in water.

Beautiful rock crystals occur in veins in the corries.

Cesena and Perticara are well-known localities in this district, the latter yielding crystals coated with asphalt.

Starch grains may often be seen in contact with the pigment crystals.

It is the methyl ester of a neutral body colchicein, which may be obtained in white acicular crystals.

The potassium salt, after recrystallization from warm water, separates in large tabular crystals.

The solution obtained may be evaporated in vacuo until it attains a density of 1.46 when, if partially saturated with potassium hydroxide and filtered, it yields crystals of potassium pentathionate, K 2 S 5 0 6.3H 2 0.

While polysymmetry is solely conditioned by the manner in which the mimetic twin is built up from the single crystals, there being no change in the scalar properties, and the vector properties being calculable from the nature of the twinning, in the case of polymorphism entirely different structures present themselves, both scalar and vector properties being altered; and, in the present state of our knowledge, it is impossible to foretell the characters of a polymorphous modification.

This cools and stirs the lead when crystals begin to form.

The habit of the crystals may be rhombohedral, pyramidal or tabular, rarely prismatic. In fig.

The so-called "iron roses" (Eisenrosen) of Switzerland are rosette-like aggregates of hexagonal tabular crystals, from fissures in the gneissose rocks of the Alps.

Such red ore is generally neither so dense nor so hard as the crystals.

Fe3P occurs as crystals in the product of fusing iron with phosphorus; it dissolves in strong hydrochloric acid.

Kris slid two rare green life crystals across the table, the common form of payment for an assassination not ordered by Death herself.

The ceilings were gilded, the chandeliers dripping with crystals.

By either of these methods, it is obtained in the form of bronzecoloured crystals.

The liquid is precipitated by alcohol, and the washed and dried precipitate is then dissolved in water and allowed to stand, when the salt separates in dark-coloured crystals.

There have been repeated stories of diamonds obtained from the Finley Mountains (which are volcanic) in the central province, but all specimens sent home, except one, have hitherto proved to be quartz crystals.

The "crested" or "cock's comb" barytes occurs as rounded aggregations of thin lamellar crystals.

All these are strikingly alike in appearance and general characters, differing essentially only in chemical composition, and it would seem better to reserve the name cerargyrite for the whole group, using the names chlorargyrite (AgC1), embolite (Ag(Cl, Bl)), bromargyrite (AgBr) and iodembolite (Ag(C1, Br, I)) for the different isomorphous members of the group. They are cubic in crystallization, with the cube and the octahedron as prominent forms, but crystals are small and usually indistinct; there is no cleavage.

A crystal may be regarded as built up of primitive parallelepipeda, the edges of which are in the ratio of the crystallographic axes, and the angles the axial angles of the crystals.

When precipitated from solutions it forms red tetragonal crystals, which, on careful heating, give a yellow rhombic form, also obtained by crystallization from the fused substance, or by sublimation.

Many instances have been recorded where substitution has effected a deformation in one particular direction, the crystals of homologous compounds often exhibiting the same angles between faces situated in certain zones.

More useful is the property of isomorphous substances of forming mixed crystals, which are strictly isomorphous with their constituents, for all variations in composition.

In such crystals each component plays its own part in determining the physical properties; in other words, any physical constant of a mixed crystal can be calculated as additively composed of the constants of the two components.

In these two instances the component crystals are miscible in all proportions; but this is by no means always the case.

It may happen that the crystals do not form double salts, and are only miscible in certain proportions.

Magnesium sulphate (orthorhombic) takes up ferrous sulphate (monoclinic) to the extent of 19%, forming isomorphous orthorhombic crystals; ferrous sulphate, on the other hand, takes up magnesium sulphate to the extent of 54% to form monoclinic crystals.

An important distinction separates true mixed crystals and crystallized double salts, for in the latter the properties are not linear functions of the properties of the components; generally there is a contraction in /10.591 volume, while the re fractive indices and other physical properties do not, in general, obey the additive law.

He also engaged in work on magnetism, the polarization of light, phosphorescence and the absorption of light in crystals.

Babingtonite is found as small black crystals on felspar in the granite of Baveno in Italy, and in the Haytor iron mine in Devonshire.

Few obsidians are entirely vitreous; usually they have small crystals of felspar, quartz, biotite or iron oxides, and when these are numerous the rock is called a porphyritic obsidian (or hyalo-liparite).

These crystals have, as a rule, very good crystalline form, but the quartz and felspar are often filled with enclosures of glass.

Their lustre is vitreous except when they contain many minute crystals; they are then velvety or even resinous in appearance.

When crystals are present they generally have their long axes parallel to the fluxion.

Even when conspicuous and well formed crystals are not visible in the rock there is nearly always an abundance of minute imperfect crystallizations (microlites, &c.).

The larger ones polarize light, have angular outlines like those of crystals, and may even show twinning and definite optical properties by which they can be identified as belonging to felspar, augite or some other rock-forming mineral.

Porphyritic crystals often contract less than the surrounding glass, which accordingly becomes strained, and in polarized light may show a weak double refraction in a limited area surrounding the crystal.

Occasionally the rounded cracks extend from the matrix into some of the crystals especially those of quartz which have naturally a conchoidal fracture.

By many lines of evidence we are led to believe that obsidians in course of time suffer devitrification, in other words they pass from the vitreous into a crystalline state, but as the changes take place in a solid mass they require a very long time for their achievement, and the crystals produced are only of extremely small size.

They all crystallize in the monoclinic system, often, however, in forms closely resembling those of the rhombohedral or orthorhombic systems. Crystals have usually the form of hexagonal or rhomb-shaped scales, plates or prisms, with plane FIG.

The best developed crystals are those of Vesuvian biotite.

Flattened crystals of garnet, films of quartz, and needles of tourmaline are not uncommon.

Artificially formed crystals of the various species of mica have been observed in furnace-slags and in silicate fusions.

The best crystallized specimens of any mica are afforded by the small brilliant crystals of biotite, which encrust cavities in the limestone blocks ejected from Monte Somma, Vesuvius.

This resolution of the original wave is the well-known "Principle of Huygens," and by its means he was enabled to prove the fundamental laws of optics, and to assign the correct construction for the direction of the extraordinary ray in uniaxial crystals.

To the kettle, two-thirds full of crystals of lead, is now added lead of the same tenor in silver, the whole is liquefied, and the cooling, crystallizing, skimming and ladling are repeated.

As soon as two-thirds of the lead has separated in the form of crystals, the steam is shut off and the liquid lead drained off through the two spouts into the moulds.

The fire underneath the pot is again started, the crystals are liquefied, and one of the two pans, filled with melted lead, is tilted by means of the crane and its contents poured into the pot.

Lead nitrate, Pb(N03)2, is obtained by dissolving the metal or oxide in aqueous nitric acid; it forms white crystals, difficultly soluble in cold water, readily in hot water and almost insoluble in strong nitric acid.

It forms colourless transparent crystals, soluble in one and a half parts of cold water and in eight parts of alcohol, which on exposure to ordinary air become opaque through absorption of carbonic acid, which forms a crust of basic carbonate.

In anisotropic bodies, such as crystals, the direction of the magnetization does not in general coincide with that of the magnetic force.

The solution turns yellow in colour, and, when saturated, deposits a pasty mass of crystals.

These are filtered off hot, and the filtrate is allowed to cool, when crystals of the uranate separate out.

But the increase of size which constitutes growth is the result of a process of molecular intussusception, and therefore differs altogether from the process of growth by accretion, which may be observed in crystals and is effected purely by the external addition of new matter - so that, in the well-known aphorism of Linnaeus, the word "grow" as applied to stones signifies a totally different process from what is called "growth" in plants and animals.

The whole is then left to itself, when crystals of tin gradually separate out on the bottom of the basin.

This structure can be rendered visible by superficial etching with dilute acid; and as the minuter crystals dissolve more quickly than the larger ones, the surface assumes a frosted appearance (moiree metallique).

The chloride readily combines with water to form a crystallizable hydrate SnCl 2.2H 2 O, known as "tin salt" or "tin crystals."

The crystals are very soluble in cold water, and if the salt is really pure a small proportion of water forms a clear solution; but on adding much water most of the salt is decomposed, with the formation of a precipitate of oxychloride, 2Sn(OH)Cl H20.

According to Michel and Kraft, one litre of cold saturated solution of tin crystals weighs 1827 grammes and contains 1333 grammes of SnCl 2.

The same oxychloride is produced when the moist crystals, or their solution, are exposed to the air.

Hence all tin crystals as kept in the laboratory give with water a turbid solution, which contains stannic in addition to stannous chloride.

A strip of metallic zinc when placed in a solution of stannous chloride precipitates the tin in crystals and takes its place in the solution.

The haematoidin pigment may vary in colour from yellowish or orange-red to a ruby-red, and forms granular masses, rhombic prisms or acicular crystals.

These crystals are extremely resistant to absorption, are found in old blood clots, and have been known to persist in old cerebral haemorrhages after many years.

He also devoted much attention to the pyroelectric phenomena of crystals, which served as the theme of one of the two memoirs he presented for the degree of D.Sc. in 1869, and to the determination of crystallographic constants.

A similar glass, if its cooling is greatly retarded, produces throughout its substance minute crystals of metallic copper, and closely resembles the mineral called avanturine.

The refractive indices of all glasses at present available lie between 1.46 and 1 90, whereas transparent minerals are known having refractive indices lying considerably outside these limits; at least one of these, fluorite (calcium fluoride), is actually used by opticians in the construction of certain lenses, so that probably progress is to be looked for in a considerable widening of the limits of available optical materials; possibly such progress may lie in the direction of the artificial production of large mineral crystals.

From the alloy containing 25% of silicon, the excess of magnesium is removed by a mixture of ethyl iodide and ether and a residue consisting of slate-blue octahedral crystals of magnesium silicide is left.

These frozen metals in general form compact masses consisting of aggregates of crystals belonging to the regular or rhombic or (more rarely) the quadratic system.

Gold, silver, copper, lead, aluminium, cadmium, iron (pure), nickel and cobalt are practically amorphous, the crystals (where they exist) being so closely packed as to produce a virtually homogeneous mass.

Regular crystals expand equally in all directions; rhombic and quadratic expand differently in different directions.

Hence, supposing the crystals immediately after their formation to be in absolute contact with one another all round, then, in the case of Class II., such contact will be maintained on cooling, while in the case of Class I.

The curing or preparation of the crystals for the market by separating the molasses from them.

It is found that in reducing the juice of these two qualities to syrup, fit to pass to the vacuum pans for cooking to crystals, the total amount of evaporation from the degraded j uice is about half that required from the normal juice produced by double crushing.

The choice of the size of the crystals to be produced in a given pan depends upon the market for which they are intended.

The crystallized sugar from the vacuum pan has now to be separated from the molasses or mother-liquor surrounding the crystals.

The moisture from the clay, percolating through the mass of sugar, washes away the adhering molasses and leaves the crystals comparatively free and clear.

Thus also the crystals already formed come in contact with fresh mother-liquor, and so go on adding to their size.

The use of multiple-effect evaporation made it possible to raise the steam for all the work required to be done in a well-equipped factory, making crystals, under skilful management, by means of the bagasse alone proceeding from the.

The filtered liquors, being collected in the various service tanks according to their qualities, are drawn up into the vacuum pans and boiled to crystals.

Granulated sugar, so called, is made by passing the crystals, after leaving the centrifugals, through a large and slightly inclined revolving cylinder with a smaller one inside heated by steam.

The firstmentioned process consists of charging and feeding the vacuum pan with the richest syrup, and then as the crystals form and this syrup becomes thereby less rich the'pan is fed with syrup of lower richness, but still of a richness equal to that of the mother-liquor to which it is added, and so on until but little mother-liquor is left, and that of the poorest quality.

Suitable provision is made for the egress of syrup from the massecuite in the cells when undergoing purging in the centrifugal; and the washing of the crystals can be aided by the injection of refined syrup and completed by that of " clairce."

As found in nature, saltpetre generally forms aggregates of delicate acicular crystals, and sometimes silky tufts; distinctly developed crystals are not found in nature.

When crystallized from water, crystals belonging to the orthorhombic system, and having a prism angle of 61 0 10', are obtained; they are often twinned on the prism planes, giving rise to pseudo-hexagonal groups resembling aragonite.

The caliche is worked up in loco for crude nitrate by extracting the salts with hot water, allowing the suspended earth to settle, and then transferring the clarified liquor, first to a cistern where it deposits part of its sodium chloride at a high temperature, and then to another where, on cooling, it yields a crop of crystals of purified nitrate.

There are perfect cleavages parallel to the rhombohedral faces, and the crystals exhibit a strong negative double refraction, like calcite.

In 1822 Wollaston examined a specimen of those beautiful copper-like crystals which are occasionally met with in iron-furnace slags, and declared them to be metallic titanium.

This view had currency until 1849, when Wohler showed that the crystals are a compound, Ti(CN)2.3T13N2, of a cyanide and a nitride of the metal.

The crystals are collected, washed, pressed and recrystallized, whereby the impurities are easily removed.

Titanium monoxide, TiO, is obtained as black prismatic crystals by heating the dioxide in the electric furnace, or with magnesium powder.

The ordinary hydrated variety forms quadratic crystals and behaves as a strong base.

Thus, for instance, near Nikko in the upper valley of the Daiya-gawa, and in several other places in the neighboring mountains, a granite-porphyry appears with large, pale, flesh-colored crystals of orthoclase, dull triclinic feispar, quartz and hornblende.

From the mine of Ichinokawa in Shikoku come the wonderful crystals of antimonite, which form such conspicuous objects in the mineralogical cabinets of Europe.

This halt in the cooling, due to the heat evolved in the solidification of the first crystals that form in the liquid, is called the freezingpoint of the mixture; the freezing-point can generally be observed with considerable accuracy.

All the mixtures whose composition lies between that of A and C deposit crystals of pure.

This process goes on until the state of the remaining liquid is represented by the point C. Now crystals of B begin to form, simultaneously with the A crystals, and the composition of the remaining liquid does not alter as the solidification progresses.

The two sloping lines cutting at the eutectic point are the freezing-point curves of alloys that, when they begin to solidify, deposit crystals of lead and tin respectively.

In the case of this pair of metals, or indeed of any metallic alloy, we cannot see the crystals forming, nor can we easily filter them off and examine them apart from the liquid, although this has been done in a few cases.

If we examine alloys on the tin side we shall find large crystals of tin embedded in the same complex.

We can sometimes obtain definite compounds in a pure state by the action of appropriate solvents which dissolve the rest of the alloy and do not attack the crystals of the compound.

It is probable that all the alloys of compositions between B and D, when they begin to solidify, deposit crystals of the compound; the lower eutectic B probably corresponds to a solid complex of mercury and the compound.

It also possesses a splendid purple Here, the large dark masses are the silver or silver-rich substance that crystallized above the eutectic temperature, and the more minute black and white complex represents the eutectic. It is not safe to assume that the two ingredients we see are pure silver and pure copper; on the contrary, there is reason to think that the crystals of silver contain some copper uniformly diffused through them, and vice versa.

We thus learn that the bronzes referred to above, although chemically uniform when solid, are not so when they begin to solidify, but that the liquid deposits crystals richer in copper than itself, and therefore that the residual liquid becomes richer in tin.

Consequently, as the final solid is uniform, the crystals formed at first must change in composition at a later stage.

For example, the compound Cu3Sn is not indicated in the freezing-point curve, and indeed a liquid alloy of this percentage does not begin to solidify by the formation of crystals of Cu 3 Sn; the liquid solidifies completely to a uniform solid solution, and only at a lower temperature does this change into crystals of the compound, the transformation being accompanied by a considerable evolution of heat.

Alloys represented by points on Ee, when they begin to solidify, deposit crystals of lead and bismuth simultaneously; Ee is a eutectic line, as also are E'e and E"e.

Among objects used are a pool of ink in the hand (Egypt), the liver of an animal (tribes of the North-West Indian frontier), a hole filled with water (Polynesia), quartz crystals (the Apaches and the Euahlayi tribe of New South Wales), a smooth slab of polished black stone (the Huille-che of South America), water in a vessel (Zulus and Siberians), a crystal (the Incas), a mirror (classical Greece and the middle ages), the finger-nail, a swordblade, a ring-stone, a glass of sherry, in fact almost anything.

Owing to the softness of the metal, large crystals are rarely well defined, the points being commonly rounded.

Except in the larger nuggets, which may be more or less angular, or at times even masses of crystals, with or without associated quartz or other rock, gold is generally found bean-shaped or in some other flattened form, the smallest particles being scales of scarcely appreciable thickness, which, from their small bulk as compared with their surface, subside very slowly when suspended in water, and are therefore readily carried away by a rapid current.

With 10% of gold present the amalgam is fluid, and with 12.5% pasty, while with 13% it consists of yellowish-white crystals.

Matthiessen and Bose obtained large crystals of the alloy Au 2 Sn 5, having the colour of tin, which changed to a bronze tint by oxidation.

By crystallizing an aqueous solution, red crystals of AuC1 3.2H 2 O are obtained.

The acid, auricyanic acid, 2HAu (CN) 4.3H20, is obtained by treating the silver salt (obtained by precipitating the potassium salt with silver nitrate) with hydrochloric acid; it forms tabular crystals, readily soluble in water, alcohol and ether.

Moseley, shortly after the discovery of the diffraction of X-rays by crystals, set to work to examine the X-ray spectrum of a number of elements each of which he made in turn the target of an X-ray tube.

Bismuth trifluoride, BiF3, a white powder, bismuth tribromide, BiBr 3, golden yellow crystals, bismuth iodide, Bi13, greyish-black crystals, are also known.

Methods depending on the free suspension of the solid in a liquid of the same density have been especially studied by Retgers and Gossner in view of their applicability to density determinations of crystals.

When heated in a current of hydrogen it sublimes in the form of brilliant prismatic crystals.

By heating with sodium amalgam and separating with hydrochloric acid, the dichloride, TaC1 2.2H 2 O, is obtained as emerald green hexagonal crystals.

Derived products in the form of crystals of phillipsite are not uncommon, but the most abundant of all are the incrustations of manganese oxide, as to the origin of which Murray and Renard are not fully clear.

After long continued frost the last of the included brine may be frozen and the salts driven out in crystals on the surface; these crystals are known to polar explorers by the Siberian name of rassol.

The crystals are orthorhombic, with angles similar to those of marcasite; they are often prismatic in habit, and the prism M is usually terminated by the deeply striated faces of an obtuse dome r.

Mispickel occurs in metalliferous veins with ores of tin, copper, silver, &c. It is occasionally found as embedded crystals, for example, in serpentine at Reichenstein, Silesia.

This variety forms a passage to the species glaucodote, (Co,Fe)AsS, which is found as well-developed orthorhombic crystals in copper ore at Hakansboda in Ramberg parish, Vestmanland, Sweden.

The crystals look like antimony, and are brittle, and so hard as to scratch glass and rubies; their specific gravity is 4.25.

The filtrate on cooling deposits crystals of potassium zirconofluoride, K 2 ZrF 6, which are purified by crystallization from hot water.

Hairy considered the crystals to be only distorted cubic forms.

Apart from crystalline form, the external characters of marcasite are very similar to those of pyrites, and when distinct crystals are not available the two species cannot always be easily distinguished.

About 15% of a volatile oil is obtained by distilling cubebs with water; after rectification with water, or on keeping, this deposits rhombic crystals of camphor of cubebs, C 15 H 26 O; cubebene, the liquid portion, has the formula C15HV4.

Subsequently he studied the expansion of solids by heat, and applied the phenomena of interference of light to the measurement of the dilatations of crystals.

Aqueous solutions deposit crystals containing 2, 4 or 6 molecules of water.

Hot or dilute cold solutions deposit minute orthorhombic crystals of aragonite, cold saturated or moderately strong solutions, hexagonal (rhombohedral) crystals of calcite.

Aragonite is the least stable form; crystals have been found altered to calcite.

Crystals may be obtained by heating di-calcium pyrophosphate, Ca2P207, with water under pressure.

The sulphydrate or hydrosulphide, Ca(SH)2, is obtained as colourless, prismatic crystals of the composition Ca(SH) 2.6H 2 O, by passing sulphuretted hydrogen into milk of lime.

Calcium metasilicate, CaSiO 3, occurs in nature as monoclinic crystals known as tabular spar or wollastonite; it may be prepared artificially from solutions of calcium chloride and sodium silicate.

Ammonia is found in small quantities as the carbonate in the atmosphere, being produced from the putrefaction of nitrogenous animal and vegetable matter; ammonium salts are also found in small quantities in rain-water, whilst ammonium chloride (sal-ammoniac) and ammonium sulphate are found in volcanic districts; and crystals of ammonium bicarbonate have been found in Patagonian guano.

It forms colourless crystals which are soluble in water and decompose on heating, with the formation of nitrogen.

It forms monosymmetric crystals which by boiling with water yield amidosulphonic acid.

With all the important work he accomplished in physics - the enunciation of Boyle's law, the discovery of the part taken by air in the propagation of sound, and investigations on the expansive force of freezing water, on specific gravities and refractive powers, on crystals, on electricity, on colour, on hydrostatics, &c. - chemistry was his peculiar and favourite study.

When dissolved in water it yields some NaOH and H202; on crystallizing a cold 'solution Na202.8H20 separates as large tabular hexagonal crystals, which on drying over sulphuric acid give Na 2 0 2.2H 2 0; the former is also obtained by precipitating a mixture of caustic soda and hydrogen peroxide solutions with alcohol.

Common washing soda or soda-crystals is the decahydrate, Na2C03 IoH 2 O, which appears as large clear monoclinic crystals.

These crystals may be half an inch to several inches in length; they are usually more or less completely weathered to white mica and kaolin.

Further, unlike diamond, it never occurs as distinctly developed crystals, but only as imperfect six-sided plates and scales.

A deep red solution was obtained, but the free quinone was not isolated since the solution on standing deposits nearly black crystals of dihydroxyphenylhydroxybenzoquinone (HO)2C6H3 C6H202.OH.

The cadmium sulphate solution must be saturated and have free crystals of the salt in it.

For the zinc solution, take 55.5 parts by weight of crystals of zinc sulphate (ZnS0470H2) and dissolve in 44.5 p arts by weight of distilled water; the resulting FIG.

For the sulphate of copper solution, take 16.5 parts by weight of pure crystals of copper sulphate (CuSO 4 50H 2) and dissolve in 83.5 parts by weight of water; the resulting solution should have a specific gravity of 1.

It is a dark yellow powder, which fuses at a high temperature, the liquid on cooling depositing shining tabular crystals; at a white heat it loses oxygen and yields the monoxide.

Iodine dissolves in an aqueous solution of the salt to form a dark brown liquid, which on evaporation over sulphuric acid gives black acicular crystals of the tri-iodide, K1 3.

Potassium sulphide, K 2 S, was obtained by Berzelius in pale red crystals by passing hydrogen over potassium sulphate, and by Berthier as a flesh-coloured mass by heating the sulphate with carbon.

It is readily soluble in water, and on evaporation in a vacuum over caustic lime it deposits colourless, rhombohedral crystals of 2KHS.H 2 0.

Potassium sulphite, K 2 S0 3, is prepared by saturating a potash solution with sulphur dioxide, adding a second equivalent of potash, and crystallizing in a vacuum, when the salt separates as small deliquescent, hexagonal crystals.

The very beautiful (anhydrous) crystals have the habit of a double six-sided pyramid, but really belong to the rhombic system.

Guvacine, named from "guvaca," an Indian designation of the betel palm, forms white crystals.

Twinned crystals are not common, but the presence of polysynthetic twinning is sometimes shown by fine striations running diagonally or obliquely across the cleavage surfaces.

Good crystals have also been obtained as a furnace product.

Wood has studied the iridescent colours seen when a precipitate of potassium silicofluoride is produced by adding silicofluoric acid to a solution of potassium chloride, and found that they are due to the same cause, the refractive index of the minute crystals precipitated being about the same as that of the solution, which latter can be varied by dilution.

The free acid forms dark red deliquescent crystals and is obtained by decomposing the silver salt with hydrochloric acid, or the barium salt with dilute sulphuric acid.

They are composed of crystals of bile-fat, cholesterine.

Many of the crystals are parti-coloured, the blue being distributed in patches in a colourless or yellow stone; but by skilful cutting, the deep-coloured portion may be caused to impart colour to the entire gem.

They occur, with many other gem-stones, as pebbles or rolled crystals in alluvial deposits of sand and gravel; the gem-gravel being known locally as illam.

Madagascar yields sapphires generally of very deep colour, occurring as rolled crystals.

The rolled crystals of sapphire occur, with garnet and other minerals, in glacial deposits, and have probably been derived from dykes of igneous rocks, like andesite and lamprophyre.

The Helena crystals are of tabular habit, being composed of the basal pinacoid with a very short hexagonal prism, whilst at Yogo Gulch many of the crystals affect a rhombohedral habit.

Occasionally monoclinic crystals are obtained by crystallizing from a strong solution.

It contains, in addition to tannin, a peculiar principle called larixin, which may be obtained in a pure state by distillation from a concentrated infusion of the bark; it is a colourless substance in long crystals, with a bitter and astringent taste, and a faint acid reaction; hence some term it larixinic acid.

In the amorphous state it is a dull green, almost infusible powder, but as obtained from chromium oxychloride it is deposited in the form of dark green hexagonal crystals of specific gravity 5 2.

Chromium trioxide, Cr03, is obtained by adding concentrated sulphuric acid to a cold saturated solution of potassium bichromate, when it separates in long red needles; the mother liquor is drained off and the crystals are washed with concentrated nitric acid, the excess of which is removed by means of a current of dry air.

Chromous sulphate, CrS04 7H 2 0, isomorphous with ferrous sulphate, results on dissolving the metal in dilute sulphuric acid or, better, by dissolving chromous acetate in dilute sulphuric acid, when it separates in blue crystals on cooling the solution.

Chromic sulphate, Cr2(S04)3, is prepared by mixing the hydroxide with concentrated sulphuric acid and allowing the mixture to stand, a green solution is first formed which gradually changes to blue, and deposits violet-blue crystals, which are purified by dissolving in water and then precipitating with alcohol.

It forms brown crystals.

It occurs in small yellowish crystals, which are turned red by exposure to light or air.

The crystals are purified by recrystallization from water.

The four phases are (I) crystals of salt, (2) crystals of ice, (3) a saturated solution of the salt in water, and (4) the vapour, which is that practically of water alone, since the salt is non-volatile at the temperature in question.

At that temperature crystals of the anhydrous Na 2 SO 4 appear, and a new fixed equilibrium exists between the four phases - hydrate, anhydrous salt, solution and vapour.

When this process is complete the temperature rises, and we pass along a new curve giving the equilibrium between anhydrous crystals, solution and vapour.

In one case (represented by the point A in the figure) the solid which freezes out is a conglomerate of crystals of the compound with those of antimony, in the other case C with those of copper.

Still further evaporation causes these crystals to effloresce and pass into the anhydrous salt.

Crystals of ice may lie side by side with crystals of common salt, but each crystalline individual is either ice or salt; no one crystal contains both components in proportions which can be varied continuously.

But, in other cases, crystals are known in which both components may enter.

Such structures are known as mixed crystals or solid solutions.

Hence the conditions necessary to secure equilibrium when the solid phase is present are not the same as those necessary to cause crystallization to start in a number of crystals at first excessively minute in size.

If a solution of a salt be stirred as it cools in an open vessel, a thin shower of crystals appears at or about the saturation temperature.

These crystals grow steadily, but do not increase in number.

From this and other evidence it has been shown that the first thin shower in open vessels is produced by the accidental presence of tiny crystals obtained from the dust of the air, while the second dense shower marks the point of spontaneous crystallization, where the decrease in total available energy caused by solidification becomes greater than the increase due to the large surface of contact between the liquid and the potentially existing multitudinous small crystals of the shower.

If the temperature at which this dense spontaneous shower of crystals is found be determined for different concentrations of solution, we can plot a "supersolubility curve," which is found generally to run roughly parallel to the "solubility curve" of steady equilibrium between liquid and already existing solid.

The 20 40 60 80 100 liquid then becomes saturated with B also, and, if inoculated with B crystals, will deposit B alongside of A, till the whole mass is solid.

But, if no solid be present initially, or if the cooling be rapid, the liquid of composition x becomes supersaturated and may cool till the supersaturation curve is reached at b, and a cloud of A crystals comes down.

The conditions may then remain those of equilibrium along the curve f E, but before reaching f the solution may become supersaturated with B and deposit B crystals spontaneously.

Many deposits of limonite have been found, on being worked, to pass downwards into ferrous carbonate; and crystals of chalybite converted superficially into limonite are well known.

But it is obvious that certain distributions will predominate, for the crystals will tend to fall so as to offer the least resistance to their motion; a needle-shaped crystal tending to keep its axis vertical, a plate-shaped crystal to keep its axis horizontal.

Potassium aluminate, K 2 Al 2 0 4, is obtained in solution by dissolving aluminium hydrate in caustic potash; it is also obtained, as crystals containing three molecules of water, by fusing alumina with potash, exhausting with water, and crystallizing the solution in vacuo.

On heating, the crystals lose water, swell up, and give the anhydrous sulphate, which, on further heating, gives alumina.

Aluminium nitride (A1N) is obtained as small yellow crystals when aluminium is strongly heated in nitrogen.

The nitrate, Al(N03)3, is obtained as deliquescent crystals (with 81120) by evaporating a solution of the hydroxide in nitric acid.

It forms small crystals, showing a brilliant green reflex, and is soluble in water and alcohol with formation of a deep red solution.

Among those directly visible to the microscope are oil drops, often coloured (Uredineae) crystals of calcium oxalate (Phallus, Russula), proteid crystals (Mucor, Pilobolus, &c.) and resin (Polyporei).

The majority of minerals are found commonly in masses which can with difficulty be recognized as aggregates of crystalline grains, and occur comparatively seldom as distinct crystals; but the diamond is almost always found in single crystals, which show no signs of previous attachment to any matrix; the stones were, until the discovery of the South African mines, almost entirely derived from sands or gravels, but owing to the hardness of the mineral it is rarely, if ever, water-worn, and the crystals are often very perfect.

Crystals belonging to the cubic system should not be birefringent unless strained; diamond often displays double refraction particularly in the neighbourhood of inclusions, both liquid and solid; this is probably due to strain, and the spontaneous explosion of diamonds has often been observed.

Bort (or Boart) is the name given to impure crystals or fragments useless for jewels; it is also applied to the rounded crystalline aggregates, which generally have a grey colour, a rough surface, often a radial structure, and are devoid of good cleavage.

The best glaziers' diamonds are chosen from crystals such that a natural curved edge can be used.

African mines the diamonds are not only crystals of various weights from fractions of a carat to 150 carats, but also occur as microscopic crystals disseminated through the blue ground.

The stones, however, are good; since they differ somewhat from the Kimberley crystals it is probable that they were not derived from the present pipes.

At Sao Joao da Chapada, in Minas Geraes, diamonds occur in a clay interstratified with the itacolumite, and are accompanied by sharp crystals of rutile and haematite in the neighbourhood of decomposed quartz veins which intersect the itacolumite.

The boulder is a crystalline rock consisting of pyroxene (chrome-diopside), garnet, and a little olivine, and is studded with diamond crystals; a portion of it is preserved in the British Museum (Natural History).

The felspathoid minerals, sodalite, haiiyne and nosean, which crystallize in isometric dodecahedra, are very frequent components of the phonolites; their crystals are often corroded or partly dissolved and their outlines may then be very irregular.

Crystals of blende belong to that subclass of the cubic system in which there are six planes of symmetry parallel to the faces of the rhombic dodecahedron and none parallel to the cubic faces; in other words, the crystals are cubic with inclined hemihedrism, and have no centre of symmetry.

Crystals exhibit pyroelectrical characters, since they possess four uniterminal triad axes of symmetry.

Crystals of blende are of very common occurrence, but owing to twinning and distortion and curvature of the faces, they are often rather complex and difficult to decipher.

A pure white blende from Franklin in New Jersey is known as cleiophane; snow-white crystals are also found at Nordmark in Vermland, Sweden.

Mention may be made of the brilliant black crystals from Alston Moor in Cumberland, St Agnes in Cornwall and Derbyshire.

Yellow crystals are found at Kapnik-Banya, near Nagy-Bánya in Hungary.

By evaporation of a solution of lanthanum oxide in hydrochloric acid to the consistency of a syrup, and allowing the solution to stand, large colourless crystals of a hydrated chloride of the composition 2LaC1 3.15H 2 O are obtained.

Beryllium oxide, beryllia or glucina, BeO, is a very hard white powder which can be melted and distilled in the electric furnace, when it condenses in the form of minute hexagonal crystals.

It is deliquescent, and readily soluble in water, from which it separates on concentration in crystals of composition BeC1 2.4H 2 0.

The sulphate is obtained by dissolving the oxide in sulphuric acid; if the solution be not acid, it separates in pyramidal crystals of composition BeSO 4.4H 2 0, while from an acid solution of this salt, crystals of composition BeS04.7H 2 O are obtained.

The crystals so obtained are very unstable and decompose rapidly with evolution of carbon dioxide.

By modern mineralogists the name chalcedony is restricted to those kinds of silica which occur not in distinct crystals like ordinary quartz, but in concretionary, mammillated or stalactitic forms, which break with a fine splintery fracture, and display a delicate fibrous structure.

Certain flat oval nodules from a decomposed lava (augite-andesite) in Uruguay present a cavity lined with quartz crystals and enclosing liquid (a weak saline solution), with a movable air-bubble, whence they are called "enhydros" or water-stones.

It occurs in all degrees of purity, from that of mere salty clay to that of the most transparent crystals.

All these names are derived from the size and appearance of the crystals, their uses and the modes of their production.

The boiled salts, the crystals of which are small, are formed in a medium constantly agitated by boiling.

The time varies for the unboiled salts from twelve hours to three or four weeks, the larger crystals being allowed a longer time to form, and the smaller ones being formed more quickly.

In Britain the brine is so pure that, keeping a small stream of it running into the pan to replace the losses by evaporation and the removal of the salt, it is only necessary occasionally (not often) to reject the mother-liquor when at last it becomes too impure with magnesium chloride; but in some works the mother-liquor not only contains more of this impurity but becomes quite brown from organic matter on concentration, and totally unfit for further service after yielding but two or three crops of salt crystals.

A slight degree of acidity seems more favourable to the crystallization of salt than alkalinity; thus it is a practice to add a certain amount of alum, 2 to 12 lb per pan of brine, especially when, as in fishery salt, fine crystals are required.

In most European countries a tax is laid on salt; and the coarser as well as the finer crystals are therefore often dried so as not to pay duty on more water than can be helped.

On extending his inquiry to other aelotropic crystals he observed a similar variation, and was thus led, in 1825, to the discovery that aelotropic crystals, when heated, expand unequally in the direction of dissimilar axes.

The excess held temporarily in solution is then deposited in crystals of CaS04.2H20.

The process goes on until a relatively small quantity of water has by instalments dissolved and hydrated the 2CaSO 4 H 2 O, and has deposited CaSO 4.2H 2 O in felted crystals forming a solid mass well cemented together.

There is reason to suppose that the change described takes place in two stages, the gypsum first forming orthorhombic crystals and then crystallizing in the monosymmetric system.

Thallic chloride, T1C1 3, is obtained by treating the monochloride with chlorine under water; evaporation in a vacuum gives colourless deliquescent crystals of T1C1,.H20.

Thallic sulphate, T1 2 (SO 4) 3.7H 2 O, and thallic nitrate, Tl(NO 3) 3.8H 2 0, are obtained as colourless crystals on the evaporation of a solution of the oxide in the corresponding acid.

The hydrated chloride, MnCl2.4H2O, is obtained in rose-red crystals by dissolving the metal or its carbonate in aqueous hydrochloric acid and concentrating the solution.

It crystallizes in large pink crystals, the colour of which is probably due to the presence of a small quantity of manganic sulphate or of a cobalt sulphate.

It forms yellow crystals soluble in water; the aqueous solution on standing gradually depositing a basic salt.

It is purified by redissolving and crystallization, and is sold either in the state of crystals or finely ground.

The clear vat-liquor, if allowed to cool down to ordinary temperature, would separate out part of the sodium carbonate in the shape of decahydrated crystals.

It is continued until the contents of the pan have been coverted into a thick paste of small crystals of monohydrated sodium carbonate, permeated by a mother-liquor which is removed by draining on perforated plates or by a centrifugal machine, and is always returned to the pans.

The drained crystals are dried and heated to redness in a reverberatory furnace; when " finished," the mass is of an impure white or light yellow colour and is sold as ordinary " soda-ash."

If purer and stronger soda-ash is wanted, the boiling down must be carried out in pans fired from below, and the crystals of monohydrated sodium carbonate " fished " out as they are formed, but this is mostly done after submitting the liquor to the purifying operations which we shall now describe.

There the reaction mentioned above takes place, and Owing to the concentration of the liquid the sodium bicarbonate formed is to a great extent precipitated in the shape of small crystals, forming with the mother-liquor a thin magma.

On the other hand the cooling must not be carried too far, for in this case the crystals of sodium bicarbonate become so fine that the muddy mass is very difficult to filter.

Here a separation takes place between the crystals of sodium bicarbonate and the mother-liquor.

The reason why two levels are employed is that sometimes crystals are formed by the decomposition of the glass which cause the bubble to stick at different points and so give false readings.

It is an amorphous white powder; but it may also be obtained in crystals isomorphous with cassiterite by heating the amorphous form with borax to a very high temperature.

Thorium chloride, ThC1 4, is obtained as white shining crystals by heating a mixture of carbon and thoria in a current of chlorine.

It forms large colourless hexagonal crystals.

It occurs as large octahedral crystals often with rounded edges, and as granular masses.

Crystals are usually twinned, and are often complex and difficult to decipher.

Crystals have imperfect cleavages parallel to the eight faces of the pyramid c 12011.

It forms black lustrous crystals, or when quickly condensed, a dark green crystalline powder.

The hexachloride, WC1 6, is obtained by heating the metal in a current of dry chlorine in the absence of oxygen or moisture, otherwise some oxychloride is formed; a sublimate of dark violet crystals appear at first, but as the hexachloride increases in quantity it collects as a very dark red liquid.

The monoxychloride, WOC14, is obtained as red acicular crystals by heating the oxide or dioxychloride in a current of the vapour of the hexachloride, or from the trioxide and phosphorus pentachloride.

The dioxybromide forms light red crystals or a yellow powder; it volatilizes at a red heat, and is not acted upon by water.

Tungsten disulphide, W52, is obtained as soft black acicular crystals by the action of sulphur, sulphuretted hydrogen or carbon bisulphide on tungsten.

Here also are polished stalagmites, a rich buff slashed with white, and others, like huge mushrooms, with a velvety coat of red, purple or olive-tinted crystals.

Hence some stalactites have their tips under water long enough to allow tassels of crystals to grow on them, which, in a drier season, are again coated over with stalactitic matter; and thus singular distortions are occasioned.

Their presence is due to lateral outgrowths of crystals shooting from the side of a growing stalactite, or to deflections caused by currents of air, or to the existence of a diminutive fungus peculiar to the locality and designated from its habitat Mucor stalactitis.

He also found that the polarity which minerals receive from heat has a relation to the secondary forms of their crystals - the tourmaline, for example, having its resinous pole at the summit of the crystal which has three faces.

In the other pyro-electric crystals above mentioned, Hatly detected the same deviation from the rules of symmetry in their secondary crystals which occurs in tourmaline.

The 22nd series (1848) is occupied with the discussion of magnetocrystallic force and the abnormal behaviour of various crystals in a magnetic field.

Of other papers in which he dealt with this and kindred branches of physics may be mentioned "Observations with a Rigid Spectroscope," "Heating of a Disc by Rapid Motion in Vacuo," "Thermal Equilibrium in an Enclosure Containing Matter in Visible Motion," and "Internal Radiation in Uniaxal Crystals."

It crystallizes in the cubic system, but the crystals are often flattened, elongated, rounded or otherwise distorted.

Native silver occurs with the copper, in some cases embedded in it, like crystals in a porphyry.

It forms dark blue prismatic crystals containing 3, 4, or 6 molecules of water according to the temperature of crystallization.

Of these the chief are Poole's Hole, a vast stalactite cave, about half a mile distant; Diamond Hill, which owes its name to the quartz crystals which are not uncommon in its rocks; and Chee Tor, a remarkable cliff, on the banks of the Wye, 300 ft.

It is practically insoluble in water, and is only very slightly soluble in dilute acids; it is soluble to some extent, when freshly prepared, in hot concentrated sulphuric acid, and on cooling the solution, crystals of composition BaSO 4 H 2 SO 4 are deposited.

Crystals of ordinary borax swell up to a very great extent on heating, losing their water of crystallization and melting to a clear white glass.

The crystals of octahedral borax fuse more easily than those of the prismatic form and are less liable to split when heated, so that they are preferable for soldering or fluxing.

The deposits formed by evaporation from these lakes and marshes or salines, are mixtures of borates, various alkaline salts (sodium carbonate, sulphate, chloride), gypsum, &c. In the mud of the lakes and in the surrounding marshy soil fine isolated crystals of borax are frequently found.

For example, crystals up to 7 in.

Borax crystallizes with ten molecules of water, the composition of the crystals being Na2B407+10H20.

The crystals belong to the monoclinic system, and it is a curious fact that in habit and angles they closely resemble pyroxene (a silicate of calcium, magnesium and iron).

Distinct crystals are rarely met with; these are rhombohedral and isomorphous with arsenic and bismuth; they have a perfect cleavage parallel to the basal plane, c (111), and are sometimes twinned on a rhombohedral plane, e (1 ro).

The stibonium iodide on treatment with moist silver oxide gives the corresponding tetramethyl stibonium hydroxide, Sb(CH 3)40H, which forms deliquescent crystals, of alkaline reaction, and absorbs carbon dioxide readily.

The wealth of crystals is, however, surprising, and these are of endless variety and fantastic beauty.

Cleveland's Cabinet and Marion's Avenue, each a mile long, are adorned by myriads of gypsum rosettes and curiously twisted crystals, called "oulopholites."

Again, there are chambers with drifts of snowy crystals of the sulphate of magnesia, the ceilings so thickly covered with their efflorescence that a loud concussion will cause them to fall like flakes of snow.

The crystals are sometimes polysynthetic, a large octahedron, e.g., being built up of small cubes.

Certain crystals from Cumberland are beautifully fluorescent, appearing purple with a bluish internal haziness by reflected light, and greenish by transmitted light.

Cavities containing liquid occasionally occur in crystals of fluor-spar, notably in the greasy green cubes.

Some of the finest crystals occur in the lead-veins of the Carboniferous Limestone series in the north of England, especially at Weardale, Allendale and Alston Moor.

Devon, notably near Liskeard, where fine crystals have been found, with faces of the six-faced octahedron replacing the corners of the cube.

With concentrated nitric acid, in the presence of cold concentrated sulphuric acid, it yields trinitro-resorcin (styphnic acid), which forms yellow crystals, exploding violently on rapid heating.

The revolving band forms the cathode, and at one end makes a rubbing contact with a travelling belt placed at an angle so that the crystals of silver detached thereby from the cathode are conveyed by it from the solution and deposited outside.

After twenty-four hours about one-half of the silver has separated out in crystals; from the mother-liquor the rest comes down promptly on application pf a water-bath heat.

It readily dissolves in ammonia, the solution, on evaporation, yielding rhombic crystals of 2AgC1.3NH 3; it also dissolves in sodium thiosulphate and potassium cyanide solutions.

It forms with silver nitrate the yellowish green solid, Ag 2 S AgNO 3, and with silver sulphate the orange-red powder, Ag 2 S Ag 2 SO 4 Silver sulphate, Ag 2 SO 4, is obtained as white crystals, sparingly soluble in water, by dissolving the metal in strong sulphuric acid, sulphur dioxide being evolved, or by adding strong sulphuric acid to a solution of the nitrate.

In 1821 he was busy with electrical experiments and in 1822 with investigations of the fluids contained in the cavities of crystals in rocks.

In Oxford county tourmaline, spodumene (or kunzite) and beryl occur, the tourmaline crystals being notably large and beautiful.

Confusion has arisen in regard to this point from attempts to compare organized bodies with crystals, the comparison having been suggested by the view that as crystals present the highest type of inorganic structure, it was reasonable to compare them with organic matter.

Differences between crystals and organized bodies have no bearing on the problem of life, for organic substance must be compared with a liquid rather than with a crystal, and differs in structure no more from inorganic liquids than these do amongst themselves, and less than they differ from crystals.

Living matter is a mixture of substances chiefly dissolved in water; the comparison with the crystals has led to a supposed distinction in the mode of growth, crystals growing by the superficial apposition of new particles and living substance by intussusception.

Another method consists in mixing the powdered bark with milk of lime, drying the mass slowly with frequent stirring, exhausting the powder with boiling alcohol, removing the excess of alcohol by distillation, adding sufficient dilute sulphuric acid to dissolve the alkaloid and throw down colouring matter and traces of lime, &c., filtering, and allowing the neutralized liquid to deposit crystals.

Quinine of commerce is the neutral sulphate,C20H24N202 H2S04.8H20, which occurs in commerce in the form of very light slender white acicular crystals.

The secondary phloem contains numerous thick-walled fibres, parenchymatous cells, and large sieve-tubes with plates on the radial walls; swollen parenchymatous cells containing crystals are commonly met with in the cortex, pith and medullary-ray tissues.

The characteristic companion-cells of Angiosperms are represented by phloem-parenchyma cells with albuminous contents; other parenchymatous elements of the bast contain starch or crystals of calcium oxalate.

One of the bestknown anatomical characteristics of the genus is the occurrence of numerous spindle-shaped or branched fibres with enormouslythickened walls studded with crystals of calcium oxalate.

Usually, however, this lower degree of symmetry is not indicated by the faces developed on the crystals.

The two crystals shown in figs.

The faces s are striated parallel to their edge of intersection with r; this serves to distinguish r and z, and thus, in the absence of x faces, to distinguish leftor right-handed crystals.

Numerous other faces have been observed on crystals of quartz, but they are of rare occurrence.

Twinned crystals of quartz are extremely common, but are complex in character and can only be deciphered when the faces s and x are present, which is not often the case.

Such twins may therefore be mistaken for simple crystals unless they are attentively studied; but the twinning is often made evident by the presence of irregularly bounded areas of the duller z faces coinciding with the brighter r faces.

A similar distribution of electric charges is produced when a crystal is subjected to pressure; quartz being thus also piezo-electric. Etched figures, both natural and artificial (in the latter case produced by the action of hydrofluoric acid), on the faces of the crystals are in accordance with the symmetry, and may serve to distinguish leftand righthanded crystals.

This phenomenon is connected with the symmetry of the crystals, and is also shown by the crystals of certain other substances in which there are neither planes nor centre of symmetry.

Superimposed sections of rightand left-handed quartz, as may sometimes be present in sections of twinned crystals, exhibit Airy's spirals in the polariscope.

Many peculiarities of the growth of crystals are well illustrated by the mineral quartz.

Crystals with a helical twist are not uncommon.

Enclosures of other minerals (rutile, chlorite, haematite, gothite, actinolite, asbestos and many others) are extremely frequent in crystals of quartz.

Cavities, either rounded or with the same shape ("negative crystals") as the surrounding crystal, are also common; they are often of minute size and present in vast numbers.

The presence of these enclosed impurities impairs the transparency of crystals.

In size they vary between wide limits, from minute sparkling points encrusting rock surfaces and often so thickly clustered together as to produce a drusy effect, to large single crystals measuring a yard in length and diameter and weighing half a ton.

The characters as given above apply more particularly to crystals of quartz, but in the various massive and compact varieties the material may be quite different in general appearance.

Further, these varieties may be of almost any colour, whereas transparent crystals have only a limited range of colour, being either colourless (rock-crystal), violet (amethyst), brown (smoky quartz) or yellow (citrine).