4 PHILOSOPHICAL TRANSACTIONS. [ANNO 17 Q6. 



XII. An Analysis of the Carynthian Molybdate of Lead ; with Experiments on 

 the Molybdic Acid. To which are added some Experiments and Observations on 

 the Decomposition of the Sulphate of Ammonia. By Charles Hatchett, Esq. 

 p. 285. 



§ 1. The celebrated Scheele, in 1778, read before the Acad, of Sc. at Stockholm 

 an essay, in which he proved, by a series of experiments, that the mineral called 

 Molybdaena was composed of sulphur, and a peculiar metallic substance, which, like 

 arsenic and tungsten, was liable by super-oxygenation to be converted into a me- 

 tallic acid, which in its properties differed from every other that had been previously 

 discovered *. The experiments of M. Pelletier-j~, Mr. Islmann;};, and Mr. Hielm §, 

 confirmed the discovery of the Swedish chemist ; but the existence of this metallic 

 substance was only known to be in that mineral which Scheele had examined, as 

 no vestige of it had as yet been discovered in other bodies appertaining to the mi- 

 neral kingdom. Mr. Jacquin, in 1781 and 1786, gave to the public an account, 

 from the Abbe Wulfen, of a yellow sparry lead ore, found at Villach in Carinthia||; 

 and the Abbe Wulfen himself, in an elaborate work, written in the German lan- 

 guage, and published in 1785, also described the above-mentioned lead ore, toge- 

 ther with some experiments which had been made on it ^[. Nothing satisfactory 

 however relative to its nature was exposed in these memoirs ; and though the sub- 

 stance was indisputably proved to be an ore of lead, yet the mineralizing principle 

 of it remained unknown. 



In 1790, Mr. Heyer, of Brunswick, made some experiments on this ore; from 

 which he inferred that it was composed of lead, combined with the tungstic acid**; 

 and in the same year Mr. Klaproth communicated a similar account, which he had 

 received from Mr. Salzwedel, of Frankfort sur Mayne -\"\-. This substance was 

 therefore universally believed to be a tungstate of lead, till that excellent chemist 

 Mr. Klaproth undertook to subject it to a further examination ; and as the experi- 

 ments which I have made may be regarded as a continuation of those made by Mr. 

 Klaproth, I think it necessary here to mention them. 



Mr. Klaproth says, that by previous experiments he had found, that nitric acid 

 much diluted did not attack the ore when cold ; and therefore to separate it from 

 the soluble matrix, he successively poured small quantities of the diluted acid on 

 the ore till all effervescence had ceased, after which the ore was washed and dried. 

 The nitric acid which had been employed was found to contain calcareous earth, 

 and also a considerable quantity of red oxyde of iron, which on being dissolved in 



* Scheele's Essays, transl. by Dr. Beddoes, p. 227.. f Journ. de Phys. Dec. 1785. 



\ Chem. Ann. von Crell, 1787, et Journ. de Phys. Oct. 1788. § Journ. de Phys. Mai, 1789. ' 



|| Nic Jos. Jacquin Misc. Austr. torn. 2, p. 139 i et N. J. Jacquin Collect, torn. 1, p. 3. This ore 

 is also described in Lithophyl. Bornianum, torn. 1, p. 90; et torn 2, p. 123. — Karsten in Mus. Lesk. 

 torn. 2, p. 501. — Werner's Verziech. Band, 1, p. 128. — Raab's Catal. tome 2, p. 379. — Rome de l'lsle 

 Cristal. tome 3, p. 387. — Widenmann's Handb. der Mineralogie, p. 864. 



^f Xavier Wulfens Abhand. vom Karnthnerischen Bleyspate. Wien, 1785. 



** Chem. Ann. von Crell, 1790, p. 58. ft lbLd - l 79°> P- 297.— Orig. 



