54 WRITINGS OF JAMES SMITIISON. 



from a small aperture in the cone of Vesuvius," and which 

 I apprehend to have happened in 1792 or 1793. 



c. The masses of this salt are perfectly irregular, their 

 texture compact, their colour a clouded mixture of white,, 

 of the green of copper, and of a rusty yellow, and in some 

 places are specks and streaks of black. 



d. A fragment melted on the charcoal at the blow-pipe 

 formed hepar sulphuris. 



e. A piece weighing 9.5 grains was so strongly heated in 

 a platina crucible, that it melted and flowed level over the 

 bottom of it, but did not lose the least weight. 



/. Not the slightest fume could be perceived on holding 

 a glass tube wetted with marine acid over some of this salt,, 

 while triturating in a mortar with liquid potash ; but a sim- 

 ilar mixture being made in a bottle, and which was imme- 

 diately closed with a cork, to which was fixed a bit of red- 

 dened litmus paper, the blue colour of the paper was- 

 restored. 



g. Being dissolved in water, there was a small sandy 

 residue, which consisted of green particles of a cupreous 

 nature, of a yellow ochraceous powder, and of minute crys- 

 tals of a metallic aspect of red oxyd of iron, by which the 

 black spots in the mass had been occasioned.* Mr. KLAP- 

 BOTH found a similar admixture in muriate of soda from 

 Vesuvius, f 



h. The solution had a feeble green tint. It did not alter 

 blue or reddened turnsol paper. 



i. Prussiate of soda-and-iron threw down a small quantity 

 of red prussiate of copper from it. Liver of sulphur and 

 tincture of galls likewise caused very small precipitations. 



j. Carbonate of soda, and oxalate of potash, and solutions- 



* What mineralogists denominate speculary iron ore, Per oligiste of Mr. 

 HAUY, appears to be merely red oxyd of iron in crystals ; red hematite the 

 same substance in the state of stalactite ; and red ochres the same in a pul- 

 verulent form. The hematites which afford a yellow powder are hydrates 

 of iron. 



f Essays, Vol. II. p. 67, Eng. Trans. 



