410 MM. Svanberg and Struve on the Atomic Weight 



very of a peculiar metallic calx. This metallic calx, so termed 

 by Scheele according to the then prevailing language in che- 

 mistry, was 'said to occur in and characterise the sulphuret of 

 molybdenum. Scheele prepared the molybdena (molybdenjerd) 

 by treating the mineral with nitric acid, and showed that this 

 earth possessed the properties of an acid. It combines with 

 potash to form a salt which separates in small crystals, which 

 expels carbonic acid when treated with carbonate of potash, and 

 yields the neutral salt. In like manner it unites with the vo- 

 latile alkali, and leaves a gray powder when this compound is 

 heated, the alkali being volatilized. Scheele showed that the 

 acid was volatile, and entered into easily soluble combinations 

 with sulphuric and muriatic acids, and that these solutions rea- 

 dily assumed a blue colour when kept for some time, and also 

 when placed in contact with metals. This colour again dis- 

 appears upon the addition of some nitric acid, and Scheele 

 thence explained the phenomenon of the blue colour to be a 

 reduction, or as he expressed it, "this is owing to the circum- 

 stance that the molybdenum calx readily absorbs phlogiston." 

 Scheele showed that the molybdenum calx, which is obtained 

 by deflagrating the mineral with nitre and precipitation with 

 an acid, behaves differently from the pure acid, and proved 

 that this was owing to the retention of a small quantity of alkali. 

 He finally asserts that the mineral molybdenum consists of a 

 new metallic acid mineralized by sulphur. 



This subject engaged the attention of several chemists after 

 Scheele; however, they added very little to our knowledge of 

 the new body, but were principally engaged in confirming the 

 discoveries made by Scheele. Among these Pelletier* stands 

 first, in 1785. He could not explain the nature of graphite, 

 which mineral he likewise examined, but he showed that it 

 was perfectly distinct from molybdenum in its properties. 

 Pelletier prepared the calx by roasting the molybdenum ore, 

 and drew from his experiments the conclusion that the mineral 

 was a combination of a metal with sulphur. He was likewise 

 the first who attempted to produce molybdenum in the metal- 

 lic state, and some alloys of it with copper, iron, silver, &c. 

 Ilsemannf worked upon the same subject in 1787 } and contra- 

 dicted the statements of all former chemists respecting the 

 volatility of the molybdic acid and the presence of sulphur in 

 the mineral. This induced Pelletier to return to the subject J, 

 and so to substantiate still further his former observations. 



* Observations sur la Physique, sur VHisloire Naturelle, &c, par Rozier, 

 Mongez et De la Metherie. Paris, 1785, vol. xxvii. pp. 343, 434. 

 \ Crell's Chemische Amialen, 1787, vol. i. p. 407« 

 % Observations sur la Physique, &c, 1789, vol. xxxiv. p. 127. 



