of Molybdenum arid some of its Compounds. 411 



About the same time Heger* prepared the combinations of 

 molybdic acid with potash and soda, and stated that a portion 

 of the potash salt might be obtained in small, colourless cry- 

 stals of the form of six-sided prisms having their terminal edges 

 truncated, but that the greater portion consisted of flattened 

 prisms. He asserted, in opposition to the earlier statements, 

 that a pure acid might be prepared by precipitating the potash 

 salt with nitric acid. Ruprechtf made some experiments 

 upon molybdenum in 1790 without adding in the least to our 

 stock of knowledge. 



During this period, from 1788 to 1792, Hjelm % published 

 his experiments on molybdenum. His principal object was the 

 reduction of the acid, and the obtaining a fused regulus of 

 metal, and also its alloys with other metals ; but at the same 

 time he describes the behaviour of the acid towards several 

 metallic oxides. Hjelm's experiments clearly proved the me- 

 tallic nature of molybdenum ; and it may be said of these ex- 

 periments, that they were the last which were made with this 

 substance, according to the phlogistic theory, to decide as to 

 the distinctness of the new metal. The ease with which mo- 

 lybdic acid is reduced, the fusion to a button of the metal 

 obtained, the metallic lustre, the specific gravity and brittle- 

 ness, and the properties of the alloys were the objects of in- 

 vestigation. It will be seen from this how slow the path 

 pointed out by Scheele was generally adopted. Scheele taught 

 us the moist way, to render the metals soluble, and to ascer- 

 tain and determine from the phaenomena then presented the 

 chemical behaviour of bodies. 



In 1799 Richter§ fixed his attention especially upon the 

 blue compound of molybdenum, and showed that it might be 

 produced most easily by the action of tin upon a solution of 

 molybdic acid in muriatic acid. He prepared the compounds 

 of molybdic acid with the oxides of lead and silver, ascertained 

 their sparing solubility in water, and their ready solubility in 

 dilute nitric acid; he moreover determined the saturating 

 capacity of molybdic acid with regard to magnesia and mu- 

 riatic acid, and so prepared the way for those researches 

 which were subsequently to be carried out quantitatively. 



Thus for nearly a quarter of a century several chemists had 

 experimented upon this new metal, and nevertheless at the end 

 of this time little more was known of it than what its discoverer 



• CrelPs Chemische Annalen, 1787, vol. ii. pp. 21, 124. 



t Ibid. 1790, vol. i. p. 483 ; vol. ii. p. 3. 



% Kongl. Vet. Akad. Handl. for 1788, sid 280; 1789, sid 131,241 ; 1790, 

 sid50,81; 1791, sid G5, 213; 1792, sid 115. 



§ Ueber die neuen Gegenstande der Chemie, I. Stuck, p. 61 ; II. p. 97 > 

 X. p. 86. 



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