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Similar coprolites are found and mined in other districts of England, but they are of inferior quality, containing more oxide of iron and alumina. These give the tribasic phosphate of lime, which results from the application of sulphuric acid to the nodules, a tendency to "go back" to the insoluble condition. French nodules are of inferior quality from another cause.
The specimens shown to us sufficiently indicated that it was neither alunite, similar to the rock of Tolfa and Piombino, nor those capillary and silky salts of alkaline sulphate of alumina and magnesia that line the clefts and cavities of rocks, but real masses of native alum, with a conchoidal or imperfectly lamellar fracture.
Silica and alumina combine to make common clay, but alumina forms itself into the red ruby, the golden-tinted topaz, the violet oriental amethyst, the red, white, yellow, and violet sapphire, and the beautiful green emerald. With substances of such rare capabilities we may expect rich results in color and form. We turn now to deposits from water of these two substances, especially the first.
Platinum, alumina, and rock crystal, it is true, cannot be liquified by the most intense heat of our furnaces, but they melt like wax before the flame of the oxy-hydrogen blowpipe. On the other hand, of the twenty-eight gaseous bodies with which we are acquainted, twenty-five may be reduced to a liquid state, and one into a solid.
When you are aware that even Davy missed 16 per cent. of alumina in one of his analyses and that the chemists of the present day don't seem to have detected the potash which exists so abundantly in potato-tops, you will, I think, agree how exceedingly important it is that such analysis should be checked by others, made without any communication between the parties.
I could not produce phosphorescence distinctly, but I must remark that a decisive opinion cannot be formed until other experimenters have gone over the same ground. The powder behaved in some experiments as though it contained alumina, but it did not exhibit with sufficient distinctness the red of the latter.
Among substances not of organic origin, the most notable instances are hydrated silicic acid, and hydrated alumina, with other metallic peroxides of the aluminous class. This property of colloids enabled Mr. Graham to account for a number of special results of observation, not previously explained.
The textile fabric is drawn through the alumina solution to fill the pores and tubes of the fabric; it is then passed through a weak alkaline bath to basify or render basic the aluminium salt in the pores; and then it is finally carried into the dye-bath and heated there, in order to precipitate the colour lake in the fibre.
They then left the transformation to complete itself, and it would not take less than ten or twelve days for the sulphuret of iron to be changed to sulphate of iron and the alumina into sulphate of alumina, two equally soluble substances, the others, flint, burnt coal, and cinders, not being so.
In the case of tartar emetic, it is the tannate of antimony which remains upon the cloth, a compound of considerable stability, and almost perfectly insoluble in water; in the case of a few colors fixed by the arsenical alumina mordant, the arsenic is in an insoluble state of combination with the alumina, in fact, the poisons are in the presence of their antidotes, and not even the most scrupulous manufacturer has any fear that he is turning out goods which can be hurtful to the wearer.
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