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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.
It was also found by analysis that augite usually contained more lime, less alumina, and no fluoric acid; which last, though not always found in hornblende, often enters into its composition in minute quantity. In addition to these characters, it was remarked as a geological fact, that augite and hornblende are very rarely associated together in the same rock.
Right in the midst of this half-sad, half-sentimental reverie, she heard a familiar voice behind her say earnestly: "And allophite is the new hydrous silicate of alumina and magnesia, much resembling pseudophite, which Websky found in Silesia."
The first northern case is covered with various Sulphates, or metals in combination with sulphuric acid, exhibiting beautiful crystals and colours, including sulphate of magnesia from Oregon; sulphate of zinc, or white vitriol; sulphate of iron, or green vitriol; and the splendid blue sulphates of copper from Hungary; beautiful sulphates of lead from Anglesea; sulphates of alumina; common alum; and the splendid specimens of lazurite, or lapis-lazuli,
To another portion of the solution we will add some caustic soda, NaOH, in order to rob the normal sulphate of alumina of some of its sulphuric acid. But what has all this to do with mordanting? is possibly now the inquiry.
It was made of a substance called "alumina," and a French chemist had declared that the clay banks were full of it; and yet it cost as much as silver. It had been used in France for jewelry and knicknacks, and a rattle of it had been presented to the baby son of the Emperor of France as a great rarity.
For the highest accuracy in the determination of silica, or of iron and alumina, it is also necessary to examine for silica the precipitate produced in the filtrate by ammonium hydroxide by fusing it with acid potassium sulphate and solution of the fused mass in water.
The mouth of the northern gorge was blocked by a vein of finely crystallized carbonate of lime, containing geodes and bunches. The taste is astringent, probably from the alumina; and it is based upon outcrops of a sandy calcaire apparently fit for hydraulic cement.
A texture equally minute and complicated has been observed in the wood of large trunks of fossil trees found in the Craigleith quarry near Edinburgh, where the stone was not in the slightest degree siliceous, but consisted chiefly of carbonate of lime, with oxide of iron, alumina, and carbon.
The point at which neutralisation of an acid by alkali or vice versâ just takes place is ascertained very accurately by the use of certain sensitive colours. At first litmus and cochineal tinctures were used, but in testing crude alkalis containing alumina and iron, it was found that lakes were formed with these colours, and they become precipitated in the solution, and so no longer sensitive.
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