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XXXII. Mati-rials towards a more inthnatc KnnwIed(Te of 

 Native Mohjbdena, cnntahiing a very advanta^eojis Me- 

 thod of extracting Mohjhdic Acid from that Sidphuret* 

 By C. F. BucHOLz*. 



After the repeated labours of a great many cheinists, 

 such as Quist, Scheele, Bergman, Heycr, Ilsemann, Pelle- 

 tier, Richter, &c. on sulphurct of molybdena, both in re- 

 gard to a better method of extracting molvbdic acid from 

 that miner..!, and in regard to the phaenomcna it exhibits 

 with other bodies, one might beUeve that no further re- 

 searclies remain to be made on this subject. But by re- 

 flecting properly on what has been done, we shall soon be 

 convinced of the contrary. As my principal object in this 

 memoir is to make known a more advantageous method of 

 preparing molvbdic acid, it will be requisite, to justify the 

 necessity of such a method, to recapitulate the old and new 

 processes, in order to show their defects, and to compare 

 them afterwards with mine. 



The first process for extracting molvbdic acid from mo- 

 Ivbdena consists in separating the sulphur from the molyb- 

 dena by a strong heat, and converting the remaining metal 

 into acid by continuing to heat it in the air. The vapours 

 oi the molvbdic acid are received in a proper vessel, where 

 they arc condensed under the form of yellowish white 

 scales, which are alone considered to be molybdic acid. 

 As these scales are formed very slowly and in small quan- 

 tity, and as the volatility of the molvbdic acid m a mode- 

 rately strong heat on the one hand, and on the other the 

 property of the same acid of fusing in a very strong heat, 

 and of penetrating, during its fusion, the matter of the cru- 

 cible, render it impossible to obtain in this manner a certain 

 quantitv of acid, this method cannot in any point of view 

 be considered as advantageous or even practicable : we shall 

 therefore proceed to examine the second method. 



The second process, which like the first belongs to 

 Scheele, con:^ists in distilling oft' at different times nitric 

 acid of a moderate strength h-om molybdena until the sul- 

 phur and the metal arc both converted into acid. This ope- 

 ration re(|uires from 20 to 24 parts of nitric acid for one 

 {)art of sulphuret of molybdena, and it leaves with the n!o- 

 ybdic acid the iron and cartlis which the purest molybdena 



• Froin Scl' frcr's Alhrmrinm "Journal dcr Cbemic iSoi, no. 5. p. 4.85. 



Vol. X\T. No. 63. N always 



Auj^Uil 1803. 



