SULPHURET OF BARYTES, OR BOLOGNlAN PHOSPHORUS. 12C/

l. SULPHURET OF BARYTES,

OR

BOLOGNlAN PHOSPHORUS.

The process for preparing this phosphorus is as follows: piecesof sulphate of barytes are first made red-hot, for a few minutes,in a covered crucible, placed in the middle of a fire, and thenleft to cool. When cold they are pulverized in a stone mortar,and sifted. This powder is formed into a paste with a little mu-cilage of gum arabic, and divided into cakes, cylinders, or piecesof the thickness of a quarter of an inch. Those pieces are driedin a moderate heat, and then exposed, by degrees, to a moreviolent heat, among charcoal, in a strong drawing wind-furnace.As soon as the coals are half consumed, the furnace must befilled a second time, and the phosphorus be left undisturbed.When the coals are quite consumed the ashes must be carefullyblown off w ith a pair of bellows, and the phosphorus is found atthe bottom of the grate.

These phosphoric stones exposed for a few minutes to thelight, shine wfien taken into the dark like burning coals. Evenimmersed in water, they emit the same glowing light. Notonly this phosphorus, but likewise all other phosphori of thisclass, lose their luminous property gradually, which they how-ever regain on being heated a second time.

Rationale. ...During the process of preparing the Bolognianphosphorus a partial decomposition of the sulphuric acid of thesulphate of barytes takes place. The ignited charcoal, at a hightemperature, has a greater affinity to the oxigen of the sulphuricacid than the sulphur has, it therefore attracts it, and formscarbonic acid gas ; part of the sulphur of the sulphuric acidbecomes thus separated; it unites to the pure barytes, andforms sulphuret of barytes, which seems in this union moredisposed to decompose oxigen gas, than when single. The

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