of Molybdenum and some of its Compounds. 54-3 



passed dry air through the tube, first with the application of 

 heat, and afterwards when it had cooled ; it was then weighed. 

 This operation of roasting was repeated twice, each time 

 for half an hour, to be certain that the oxidation was com- 

 plete. The difference in the weight between the first and 

 third weighing never amounted to more than half a milli- 

 gramme, and the second and third weighings always coincided. 

 To convince ourselves finally that the whole of the sul- 

 phuret had been really converted into molybdic acid, we dis- 

 solved the acid in ammonia, and always obtained a perfectly 

 clear solution. The following are the experiments. 



Sulphuret of Molybdenum A. 



grm. percent. 



I. 1*3558 grm. MoS 2 gave l*2174molybdic acid = 897919 molybdic acid. 

 II. 1-329 11925 897291 



Sulphuret B. 



III. 1-487 grm. MoS 2 gave 1-333 molybdic acid = 89-6436 



IV. 1-4225 12761 89-7082 



V. 1-403 1-2637 900712 



VI. 1-268 1-1416 900315 



VII. 12947 11622 89-7660 



VIII. 1-4957 1 3426 897640 



IX. 1-29.9 1-1652 89-9272 



X. 1-1138 10009 898635 



We must exclude from this series of experiments as erro- 

 neous V., VI. and IX., the shaking having been omitted. 



If we compare the other seven experiments and take the 

 average, we find that 100 parts of sulphuret give 89*7523 mo- 

 lybdic acid. But before we proceed to draw further con- 

 clusions from these experiments, we must first show that the 

 artificial sulphuret used in these experiments has the same 

 constitution as the native mineral. For this purpose we have 

 analysed specimens of native sulphuret from two different lo- 

 calities in Sweden; the one was from Lindas in Smaland, and 

 the other from the district of Bohus. The analyses were 

 likewise made by roasting, and when this was finished the mo- 

 lybdic acid dissolved in ammonia, when the insoluble gangue 

 was left behind and could thus be estimated : of the sulphuret 

 from Lindas we made three determinations, viz. — 



I. 1 4847 grm. native sulphuretgave 1*3382 molybdic acid & 0-0427 gangue. 

 II. 1-400 ... ... ... 1-2599 00112 ... 



III. 2-247 ... ... ... 20235 0252 ... 



IV. 1-371 native sulphuret from Bohus gave 1*2348 grm. molybdic acid and 



0*0430 gangue. 

 We have moreover examined the artificial sulphuret ob- 

 tained by treating the neutral molybdate of potash with sul- 

 phuretted hydrogen. 



