1814.] On the Composition of Arragonite. 24/ 



Perfectly neutral nitrate of strontian is insoluble in alcohol; 

 while, on the other hand, nitrate of lime dissolves in alcohol. 

 Upon this property the author grounded his method of examining 

 whether arragonite contained any strontian. 



Even the "first trials which he made answered his expectation. 

 He employed, for the purpose, arragonite from Vcrtaison, in Au- 

 vergne, with which almost all . preceding chemical analyses had 

 been made. On the cooling of a neutral and sufficiently concen- 

 trated solution of arragonite in nitric acid, and even sometimes 

 during the evaporation, some octahedral crystals separated which 

 were insoluble in alcohol, and possessed all the properties of nitrate 

 of strontian. More than twenty experiments, made with perfectly 

 pure, and with various varieties of crystallized arragonite, gave the 

 very same result; so that there could be no doubt that arragonite 

 contains some per cents, of strontian. 



These experiments were repeated with the prismatic arragonite 

 from Migianilla in Valentia and from Molina in Arragon, with the 

 columnar arragonite from Dax in the ci-devant. Beam, from Iberge 

 in the Hartz, from Neumarkt in the Oberpfalz, and with the co- 

 lumnar and fibrous arragonite from Mordklinge in Lowenslein in 

 Swabia, and from the Faroe Islands. All these yielded the same 

 results as the arragonite of Auvergne. A portion of nitrate of 

 strontian was extracted from each. 



Iu two minerals to which the term arragonite has been applied, 

 namely, iroubloom (c'lsaiblatlie), and fibrous lime {Jbserkalke) from 

 Westphalia, no strontian was found. The iroubloom is a pure car- 

 bonate of lime, and in the fibrous lime there are some per cents, of 

 gypsum. But neither of these minerals possesses the character of 

 arragonite, while they both agree perfectly with the properties of 

 rhomboidaJ calcareous spar. 



Experiments, which the author made with a great variety of spe- 

 cimens of calcareous spar, showed that carbonate of strontian is an 

 essential constituent of arragonite : for in none of them did he find 

 the least trace of strontian. In two specimens of columnar calca- 

 reous spar, indeed, when he treated the dry nitrate of lime with 

 alcohol, a very slight muddiness took place, which was removed by 

 the addition of a few drops of water, and was not again produced 

 by the muriate of barytes. Hence it might be owing to the pre- 

 sence of an atom of strontian. But both these specimens of eal- 

 eous spar exhibited here and there traces of a conchoidal 

 fracture. 



After the author had convinced himself that arragonite differs 

 from calcareous spar, by containing as a constituent a portion of 

 f strontian, and that arragonite is in reality a triple salt, 

 he undertook the exact chemical analysis of, three of the most re- 

 markable varieties bf arragonite j namely, that from Bearn, that 



from Molina in Arragon, and that liom Auver ne. And by wtty 

 of comparison With them, he analysed tWO very pure and per.- 



transparent specimens of i »uf spwj one from Iceland, the 



