Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/451

 texture being in large masses quite opake. The colour of the witherite is white with the slightest possible, if any, tinge of yellow: its fracture is broad striated approaching to strait-foliated: it is for the most part massive. I have seen only a single specimen that presented any indications of a regular crystalline form. In other particulars it agrees with the usual descriptions of this substance.

The Anglesark witherite has been analysed by Klaproth, and besides carbonate of barytes appears to contain above two per cent. of carbonate of strontites, and a scarcely appreciable quantity of oxide of copper. The Stirian witherite, on examination by the same chemist, appears to be a pure carbonate of barytes. The presence of carbonate of strontites being a circumstance of some interest, I was induced to examine the Shropshire Witherite for the purpose of ascertaining whether in this particular it agreed with that from Lancashire.

For this purpose 200 grains were dissolved in muriatic acid, and left behind 1.8 gr. of a white powder which was sulphate of barytes.

The muriatic solution being supersaturated with ammonia was evaporated to dryness and ignited till the muriate of ammonia was driven off: the residue was redissolved in water, but left behind 1.5 gr. of a brown sediment, which on digestion with sulphuric acid was separated into 1. gr. of silex insoluble in the acid, and 0.5 gr. of alumine coloured by oxide of iron, soluble in the acid, and which deposited crystals of alum on the addition of sulphate of potash.

The purified muriatic solution was brought to the crystallizing point, and the muriate of barytes which fell down was removed: the mother-liquor was mixed with alcohol and heated, the fluid (after standing a minute to clear) was poured off, and on cooling deposited long needled crystals of muriate of strontites. Water