Totaps afd Sfda /otiftJ hi Volcanic Produflu xif 



II. 



On ihe Anatyfn of Pumic(f •which is found to contain PotnJJj; and of Bafaltes and Lava containing 



Soda. Bv Dr. KENNEDY' '*. 



o. 



'N the jth of February 1798, an analyfis of pumice was communicated to the Royal So- 

 ciety of Edinburgh by Dr. Kennedy. By this analyfis he (hewed that the pumice contained 

 potafli as one of its component parts. The fpecimen analyfed was of the common kind, 

 having a fibrous texture and a fiiky luilre. By a heat of 60' of Wedgwood, it was convert- 

 ed into a kind of glafly enamel ; and in a muffle, even at a heat of 35 or 40, was fo far 

 altered, that its fibrous texture could no longer be diftinguifhed. Befides potafli, it contain- 

 ed files, argill, and a fmall quantity of iron ; but no lime or magneCa. 



Several other varieties of the common kinds of pumice ufed in the arts, were found at 

 fufible as the fpecimen above mentioned, and gave the fame kind of glafly enamel. 



The refult of the analyfis, with refpe£l to the earths and iron, correfponds very nearly 

 ilvith the refult of Mr. Klaproth's, publiflied in the 2d vol. of his Beitrage ; only he did not 

 find potafli in the fpecimen he analyfed j in which, however, there was probably fome faline 

 fubftance ; for the fame kind of pumice melted in the porcelain furnace of Berlin ; in which 

 a compound confifting only of files, argill, and a minute portion of iron, would certainly 

 not have melted. The heat of this furnace was 1 36 of Wedgwood. — See Klap. Beytr, vol. 2d, 

 p. 88. 



On the 6th of Auguft Dr. Kennedy announced to the Society, that he had difcovered 

 mineral alkali in feveral varietiesof bafaltes or whinftone. He found by chemical analyfis, 

 that the alkali exifl;ed in thefe fubftances in a ftate of very intimate combination withthck 

 earthy bafes ; and that it was with difiiculty feparated, even by the ftrongefl: acids. 



Dr. Kennedy alfo analyfed a fpecimen of lava from iEtna, at the requeft of Sir James 

 Hall, who thought it extremely probable that alkali would be found in lava, as well as ia 

 bafaltes, on account of the great refemblance which thefe two fubftances have to each other, 

 both in external appearance and in many chemical properties. The fpecimen was broken, 

 by Sir James Hall and Dr. Hume, from the celebrated current of lava which in 1669 de- 

 ftroyed part of the town of Catania. It was found, like the bafaltes, to contain foda. 



One of the fixed alkalis, potafh, has already been difcovered in fl;ony fubftances by the 

 celebrated Mr. Klaproth, to whom the world is indebted for fo many analyfes performed 

 with the greateft flcill. The experiments above-mentioned fhow, that the other fixed 

 alkali, foda, likewife exifts in ftony fubftances. 



* Abflxail, by favour of the Author. This paper will appear in the 5th vol. of the Edhiburgh Tranfafttous, 



III, Sfc^fnmenii 



