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Iron ores and refinery cinders may indeed, if they are reduced to a very fine state of division, be commonly decomposed by boiling with hydrochloric acid with or without the addition of sulphuric acid, but the undissolved silica is generally rendered impure by manganese, which can only be removed by fusion with soda.
Hydrogen, which forms two-thirds of water, and enters into some mineral substances, is perhaps next. Nitrogen, of which the atmosphere is four-fifths composed, must be considered as an abundant substance. The metal silicium, which unites with oxygen in nearly equal parts to form silica, the basis of nearly a half of the rocks in the earth's crust, is, of course, an important ingredient.
Some, which before immersion were of a particularly flinty texture, became in a few weeks so friable that they could be broken up by the fingers. 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.
Hypersthene. Bronzite. Olivine. Olivine. The minerals which form the chief constituents of these igneous rocks are few in number. Next to quartz, which is nearly pure silica or silicic acid, the most important are those silicates commonly classed under the several heads of feldspar, mica, hornblende or augite, and olivine.
In the forests of Shupanga the Mokundu-kundu tree abounds; its bright yellow wood makes good boat-masts, and yields a strong bitter medicine for fever; the Gunda-tree attains to an immense size; its timber is hard, rather cross-grained, with masses of silica deposited in its substance; the large canoes, capable of carrying three or four tons, are made of its wood.
This is lined on the bottom and sides with a packing of fine charcoal, O, or such other material as is both a poor conductor of heat and electricity as, for example, in some cases, silica or pulverized corundum or well-burned lime and the charge, P, of ore and broken, granular, or pulverized carbon occupies the center of the box, extending between the carbon plates.
She clung to the parson as a support under both her sources of trouble, but Miss Betty ran on and back, and hither and thither, looking for the diamond. Miss Kitty and the parson looked too, and how many aggravating little bits of glass and silica, and shining nothings and good-for-nothings there are in the world, no one would believe who has not looked for a lost diamond on a high road.
"This new vicious discovery would corrupt the world of art. No, I shall never confide the secret to any one," he said slowly. It would be hard to find any one less informed about such phenomena than myself; but of course I had heard of mineral springs so saturated with silica that the leaves and twigs which fell into them were turned to stone after a time.
The living man, the light and hope of the family, is murdered; but a disciple of pure science and calm philosophy enters it, and tells its agonised members that it is folly and ignorance to indulge in such grief, for science has analysed their friend, and preserved in a series of neat phials, which they may easily carry about with them, all his constituent elements, his "essentials," his carbon, his silica, this and that gas everything, in short, which made up the substance of him whom they were accustomed to call their beloved; therefore they may "comfort one another with these words!"
It is probable that temperatures above 100°C. are not absolutely necessary to dehydrate the silica; but it is recommended, as tending to leave the silica in a better condition for filtration than when the lower temperature of the water bath is used. This, and many other points in the analysis of silicates, are fully discussed by Dr.
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