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No H2S nor sulphides were found in this water. The spring, however, is said to have at times a "sulphur odor."

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Why this spring is specially named "Magnesian" is not explained. will be noted that this spring, the coolest of the series, is proportionally richer in carbonates and poorer in sulphates than the others. This relation is shown by a comparison of the percentage columns.

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THE ESTIMATION OF ALKALIES IN SILICATES, BY THOMAS M. CHATARD.

Walter Hempel proposed (Fres. Zschr. 1881, p. 496) bismuth subnitrate as a means of decomposing silicates containing alkalies, and recommended the use of 20 parts of this salt (=10 parts of bismuth oxide) to one part of the silicate. In the Berichte d. D. Chem. Gesellsch, 1881, there is an abstract of his paper, in which is proposed the use of bismuth oxide directly.

This process has been in use in this laboratory for the past six months, and, with some modifications, has given great satisfaction. Bismuth oxide has been used instead of the subnitrate, and experience has shown that, instead of ten parts, as stated above, two parts of oxide to one part of the mineral are ample in every case in which we have employed the method.

The oxide and mineral, both finely powdered, must be most thoroughly mixed, and then heated in a platinum crucible; applying at first a gentle heat and gradually increasing to full redness, which is kept up ten to fifteen minutes. In the case of an acid silicate, complete fusion may result, while the more basic the silicate the less fusible the mixture will be. Complete decomposition has been obtained when the resulting mass was so slightly sintered together as to fall on gentle pressure into powder, none of which adhered to the crucible. It has therefore been found advantageous, in dealing with acid silicates, to add to the mixture a quantity of calcium carbonate, in weight equal to that of the mineral. This device prevents the fusion which might hinder the after treatment with acid.

After the mass has been thoroughly heated to bright redness it is allowed to cool, placed in a dish, and hydrochloric acid somewhat diluted poured over it. On heating over the water bath the mass should go into solution rapidly, leaving no residue of undecomposed mineral, which is easily distinguishble from floating flakes of silica.

If complete analysis is required, evaporate to dryness and separate the silica, as in a soda fusion, afterwards removing the bismuth by sulphureted hydrogen. If only alkalies are to be determined, add ammonia and ammonium carbonate, filter, and separate magnesia from the alkalies by any of the usual methods.

The results of this process have been very satisfactory. Out of a large number of analyses the following duplicate has been selected as being sufficient to show the accuracy of the work. It may be remarked that in the case of this margarite (a very basic silicate) the mass was but slightly sintered together.

Margarite.—Gainesville, Ga.

1.0300 grammes gave 0.0440 alkali chlorides=0.0233 Na,O=2.26 per cent. 1.0243 grammes gave 0.0435 alkali chlorides=0.0231 Na,O=2.25 per cent.

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