Why issilica diffused over the stems of wheat, grasses, canes, &c.
The original wood has been replaced by silica (SiO{2}) and stained a dark reddish brown, as shown in figure 72.
So far as my experiments have extended they have proved this, that it was not essential that the silica and gold should have been deposited at the one time in auriferous lodes.
Silica is soluble in solutions of alkaline carbonates, as shown in New Zealand geysers; the solvent action being increased by heat and pressure, so also would be the silicate or sulphide of gold.
Instances are not wanting of the growth of silicaon the sides of the drives in mines.
Nor will it satisfactorily explain the auriferous antimonial silica veins of the New England district, New South Wales, in which quantities of angular and unaltered fragments of slate from the enclosing rocks are found imbedded in the quartz.
Seeing that, in most cases, they would be hermetically enclosed in molten and quickly solidifying silica they could not be acted on to any great extent by aqueous agency.
Roasting takes the place of fine crushing, as the ore from the roasting furnace is either found somewhat spongy in texture or the grains of silica in which fine gold may be incased are split or flawed by the fire.
This is because the finer gold is locked up inside fine grains of silica and hydrated oxide of iron.
He showed that most of the earthy minerals are compounds of silica with electro-positive metallic oxides, and that silica plays the part of an acid in these minerals; and in 1823 he obtained the element silicon, the oxide of which is silica.
Silica was almost certainly an oxide; but electro-negative oxides are, as a class, acids; therefore silica was probably an acid.
Hence silica was regarded as the typical earth, until Berzelius, in 1815, proved it to be an acid.
The supposition of the acid character of silica was amply confirmed by the mineralogical analyses and experiments of Berzelius.
The silica for this glass was derived, as we have seen, from quartz pebbles, but we have no information as to the source of the other important constituent, the alkali.
The silica has at all times been derived either from solid quartz, whether in the form of rock crystal or of the white pebbles from the beds of Alpine rivers, or more often from sand obtained either by excavation or from the seashore.
This, in modern scientific language, we should express by saying that it is a combination of silica with an alkali.
Silica in any case is the essential element in glass, and in any normal glass there may be present from 60 to 75 per cent.
Note: The silica may take the form of agate, chalcedony, flint, hornstone, or crystalline quartz.
Defn: A regulus consisting essentially of nickel, obtained as a residue in fusing cobalt and nickel ores with silica and sodium carbonate to make smalt.
Defn: A mineral related to the micas, but low in silica and yielding brittle folia with pearly luster.
This mineral is pure silica and free from lime, although the sands may contain some small percentage of iron.
Combined with silica it is the chief constituent of kaolins and China clays.
The substitution of borax for a portion of the silica can also be tried and will permit the use of slightly lower firing point.
This mass is easily fusible when lead or borax is present in large proportions, more infusible or harder the more silica it contains, and very refractory if alumina is present in any quantity.
The silica forming the glassy part of the glaze is stiffened by the presence of alumina, which stops any tendency to run.
With low-firing natural clays rich in silica and iron, the craze is not of much consequence.
A mixture of egg silica or water glass with fine grog and quartz sand will stop small cracks.
The glaze requires stiffening, and the addition of ground flint or quartz, China stone or clay and felspar introduces alumina and silica and raises the fusing point.
Silica here and there shows through the beaten ground, on which grows a little grass soiled by manure.
Little by little this silica in solution was deposited on the surfaces of the sand grains, enlarging them, and at the same time binding them together.
Quartzite is sandstone in which the intergranular spaces have been filled with silica (quartz) brought in and deposited by percolating water subsequent to the accumulation of the sand.
Continued deposition of silica between and around the grains finally filled the interstitial spaces, and when this process was completed, the sandstone had been converted into quartzite.
The higher the percentage of soluble silica and alumina, the more thoroughly decomposed, in all probability, is the soil as a whole and the more readily can plants secure their nutriment from the soil.
Clay may be formed from any rock containing some form of combined silica (quartz).
The sand-forming rocks that are not capable of clay production usually consist of uncombined silica or quartz, which when pulverized by the soil-forming agencies give a comparatively barren soil.
The silica in soils is usually combined with alumina and oxide of iron; or with alumina, lime, magnesia, and oxide of iron, forming gravel and sand of different degrees of fineness.
Glasses made of silica and alkali alone are incapable of permanently resisting the action of water.
The silica is found to unite with the lead, and to liberate the alumina in the crystalline form.
This well-known substance is essentially a mixture of silicates with an excess of silica or silicic acid.
From fluor-spar (free from silicaand metallic sulphides) and oil of vitriol.
Decomposition ensues, silica being deposited in a gelatinous state, and hydrofluosilicic acid remaining in solution.
The weight in grains represents the per-centage of silica in the sample examined.
But in addition to hydrochloric acid, such a solution contains chloride of sodium, a salt which causes the silica to gelatinise when the solution is heated, and otherwise modifies its properties.
By pouring silicate of soda into diluted hydrochloric acid (the acid being maintained in large excess), a solution of silica is obtained.
If steam is afterwards introduced the solution becomes very rapid, when the pressure reaches about three atmospheres, and at the end of about three hours the silica is completely dissolved.
Silica (commonly under the form of sand) is heated with carbonate of potassa or of soda, and slaked lime or oxide of lead, until the mixture fuses, and combination takes place.
The fact that these deposits are almost exclusively residual deposits formed by the leaching of silica has an important bearing on exploration.
The United States has ample domestic supplies of silica for practically all requirements.
The solution of silica on such an immense scale as is indicated by these deposits has sometimes been questioned on the general ground that silica minerals are insoluble.
Bauxites to be of commercial grade should carry at least 50 per cent alumina, and for the making of aluminum should be low insilica though the content of iron may be fairly high.
For example, the material for silicarefractories is obtained in the United States chiefly from certain regions in Pennsylvania, Missouri, and Wisconsin.
In addition to its applications to the iron and steel industry, silica finds an almost universal use in a wide variety of structural and manufacturing operations.
Katamorphism is primarily responsible for most of the deposits of silica which are commercially used.
Silica has an important use in the form of silicabrick or "ganister" for lining furnaces and converters in which acid slags are formed.
The ore has been concentrated in the iron formation almost solely by the process of leaching of silica by surface or meteoric waters, leaving the hematite in a porous mass.
Deposits of bauxite usually contain as impurities silica (in the form of kaolin or hydrous aluminum silicate), iron oxide, and titanium minerals, in varying proportions.
The principal uses of sandstone are for building stone, crushed stone, and ganister (for silica brick and furnace-linings).
Clearer evidence of their occurrence has, however, been found in fragments of wood fossilized by silica or carbonate of lime which are sometimes met with in coal seams.
Percy, the mineral matter being also changed by the removal of silica and alkalis and the substitution of substances analogous in composition to fire-clay.
They differ chemically from the micas in containing less silica and no alkalis, and from the chlorites in containing much less water; in many respects they are intermediate between the micas and chlorites.
A few miles from Waimangu is another valley, and in it a succession of primrose-coloured terraces, which are gradually being formed of silica left by the overflow of a lake of boiling sulphur, and very pretty they are.
If silica be present, it gives the iron bead when heated with a little ferric oxide; if tin is present there is no change.
The discovery of boron by Gay Lussac and Davy in 1809 led Berzelius to investigatesilica (silex).
In the following year he announced thatsilica was the oxide of a hitherto unrecognized element, which he named silicium, considering it to be a metal.
Calcareous matter is usually entirely wanting, or present only in traces, whilst free silica is found in very variable, often considerable quantities.
Into this furnace are dropped masses of ore, and with it coke to make it hotter and limestone to carry off the silica slag, or worthless part.
Clay is a kind of earth containing mostly alumina and silica or sand, that can be mixed with water, moulded into any shape, retain that shape after it is dry, and become hard by being burned.
The per cent of silica in the ash of several common fodder plants is given below: Silica in ash of various fodder plants.
In cases of siliceous calculi, accordingly, the appropriate chemical prevention is caustic potash, which being present in the free state would attract to itself any free acid and leave the silica in its soluble condition as silicate of potash.
This agent is secreted in the urine in the form of silicate of potash and is thrown down as insoluble silica when a stronger acid displaces it by combining with the potash to its exclusion.
Another inorganic substance at times found in urinary calculi is silica (SiO{2}).
The calculi formed in part of silicademand special notice.
But if a small portion of silica should be present, then the bead becomes clear.
A platinum wire is generally used for the purpose, the end of it being first dipped in the salt which is fused into a bead, after which the silica must be added, and then the bead submitted to the flame of oxidation.
With microcosmic salt, silica forms a bead in the flame of oxidation which, while hot, is clear, while the separated silica floats in it.
Glucina only occurs in a few rare minerals, in combination with silica and alumina.
The presence of silica in a mineral can easily be ascertained by treating a small fragment in a bead of microcosmic salt.
As silica and titanic acid are the only two substances that produce a clear bead, the student, if he gets a clear bead, may almost conclude that he is experimenting with silica, titanic acid being a rare substance.
The bases will dissolve out with more or less difficulty in the salt, and the silica being insoluble will remain suspended in the bead, retaining the original form of the fragment.
The plastic clays consist of silicaand alumina chemically combined with water.
The nearest approach to the use of silica alone as a fire brick is in the case of the Welsh brick, made from the Dinas rock in the Vale of Neath.
In the chalk the silica has usually been dissolved and redeposited as flint nodules, and in the Carboniferous limestone as chert bands.
Siliceous limestones, where their silicais original and of organic origin, have contained skeletons of sponges or radiolaria.
Brother Silica Roscoe had a wife and children when freedom come on.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "silica" in a variety of sentences. We hope that you will now be able to make sentences using this word.
