462 Intelligence and Miscellaneous Articles. 



allow of the formation of a secondary product ; the same effect may- 

 be produced with carbonate of lead. — Journ. de Pharm. et de Ch., 

 Mars 1845. 



ON PIAUZITE, A MINERAL RESIN. BY M. HAIDINGER. 



Colour, blackish-brown ; streak, yellowish-brown ; massive ; lus- 

 tre, resinous ; fracture, imperfect conchoidal ; translucent on the thin 

 edges; feeble lustre in cut places ; hardness = TS ; specific gravity, 

 1-220. 



Chemical properties. — At about 590° Fahr. it inflames ; it burns 

 at a somewhat higher temperature with a peculiar aromatic smell, 

 with much flame and soot, leaving an ash. It is completely soluble 

 in aether and in potash ; it is almost entirely soluble in anhydrous 

 alcohol, but less soluble in alcohol containing water. Fuming nitric 

 acid converts the colour of the dark brown resin into yellowish- 

 brown. Heated in a glass tube, there is distilled from it a yellowish 

 oily fluid, which has an acid reaction. In its common state it con- 

 tains 3*5 per cent, of hygroscopic water; when dry it yields 5-96 

 per cent, of ash. 



It occurs in veins from one inch to two inches wide, traversing 

 brown coal and bituminous wood, in a brown coal deposit, in the 

 neighbourhood of Piauze, north of Newstadtl, in Carniola. 



Its easy inflammability, and the abundance of soot which it depo- 

 sits during burning, cause it to be used for giving the black colour 

 to cast-iron ware. — Poggendorff's Annalen. Jameson's Journal. 



ON CRYSTALS IN THE CAVITIES OF TOPAZ. BY SIR D. BREWSTER. 



The author gave a brief notice to the British Association of the 

 discovery which he had made, about twenty years ago, of two new 

 fluids in the cavities of topaz, and other minerals. 



One of these fluids is very volatile, and so expansible, that it ex- 

 pands twenty times as much as water with some increase of tempe- 

 rature. When the vacuities in the cavity which it occupies are large, 

 it passes into vapour ; and in these diff'erent states he had succeeded 

 in determining its refractive power, by measuring the angles at five 

 feet. Total reflexion takes place at the common surface of the fluid 

 of the topaz. The other fluid is of a denser kind, and occupies the 

 angles and narrow necks of cavities. The cavities, however, in 

 which the soluble crystals are contained, are of a different kind. 

 They (viz. the cavities) are imperfectly crystallized, and thus they 

 exist in specimens of topaz which contain the cavities with the two 

 new fluids ; they contain none of the volatile and expansible fluid, 

 which is doubtless a condensed gas. The crystals which occupy 

 them are flat and finely crystallized rhomboids. When heat is ap- 

 plied, they become rounded at their edges and angles, and soon dis- 

 appear. After the topaz has cooled, they again appear, at first like 

 a speck, and then recrystallize gradually, sometimes in their original 

 place, but often in other parts of the cavity, their place being de- 

 termined by the mode in which the cooling is applied. — Jameson's 

 Journal, April 1845. 



