On the acetates and other compounds of alumina / by Walter Crum.

Date:
[1853?]
Catalogue details

Licence: Public Domain Mark

Credit: On the acetates and other compounds of alumina / by Walter Crum. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    ^^^^ X.. ^ ON THE ACETATES AND OTHER COMPOUNDS OF ALUMINA.* BY WALTER CRUM, F.R.S. niESIDENT OF THE PHlLOSOPHICAi SOCIBTY OF GLASGOW. The salt from which most of the products described in the present memoir were produced, is the tersulphate of alumina, now manufactured in large quantity in the north of England, under the name of concentrated alum. It is formed by the direct action of sulphuric acid upon clay, and, after a certain purification, is evaporated and sold in cakes. The impurity which the commercial article contains in largest quantity is potash alum. To separate that substance, advantage was taken of its insolubility in a saturated solution of the tersulphate. The cake- alum was dissolved in a quantity of boiling water insufficient for its entire solution in the cold. On cooling, the excess of sulphate of alu- mina, mixed with almost the whole of the potash alum, deposited, and was separated by filtration through calico. The filtered solution was then evaporated and cooled, when the tersulphate was found to crystal- lize in granular spongy masses. It was then drained and separated as much as possible from the mother liquor by strong pressure between numerous folds of calico. The product was re-dissolved in boiling water, and again crystallized and pressed. A salt was thus obtained, having little more than traces of the arseni- ous acid and the potash of the original material, together with a little iron and chloride of sodium. It has the formula I AI2O3, 3SO3 + 18H0 first observed in 1825 by Boussingault in the hair-like substance found among the black schistus of the Andes of Columbia, near Bogota, He afterwards found the same substance in the volcano of Pasto, (north of Quito,) w:hel:e it is forriied by the action of the sulphurous vapours upon the schistus. It exists there in such quantities as to have enabled the Pastusos to become the manufacturers of chemical products for the whole country. They dissolve the alum in water, evaporate it to dryness, and form it into spherical masses like camphor, which are altogether free from iron. The same substance is formed in this neighbourhood from a schistus containing pyrites, in which case it is mixed or combined with sulphate of iron. Read before the Philosophical Society of Glasgow, April 27th, 1853.