502 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.47. 



both the residue and the distillate through the whole course of 

 analysis. 



The method of fusion with sodium carbonate as outlined by Tread- 

 well ^ was therefore adopted, although modifications had to be 

 introduced to obtain the copper in No. 2. The rare metals were 

 also separated by the course recommended by Treadwell, that of 

 decomposition by nitro-hydrochloric acid. It was found that on 

 washing the residue insoluble in ammonia with pure water, the 

 oxides of columbium and tantalum tended to become colloidal and 

 run through the filter paper, a turbid filtrate under these con<litions 

 constituting a very delicate test for their presence; adding a little 

 amLmoiiium nitrate to the wash water coagulated them again, how- 

 ever, and permitted their retention on the filter. 



In sample 1 the unusually high value of 0.80 was obtained for 

 calcium. As it seemed of interest to know whether this was due to 

 included calcite gangue, or to scheelitc, half a gram was ignited for 

 30 minutes in a platinum crucible at the highest temperature of a 

 modern complete combustion burner, and tested with neutral phe- 

 nolphthalein solution. Not the slightest alkalinity was shown, 

 although calcite should have been readily decomposed under these 

 conditions. It was then thought that treatment with tartaric acid 

 might throw some light on the question. Half a gram of the sample 

 was heated on a steam bath with a solution of 10 grams of tartaric 

 acid in 50 cc. of water for three hours, the undecomposed mineral 

 filtered out, and ammonimn hydroxide and ammonium oxalate 

 added to the filtrate. On standing overnight a precipitate of cal- 

 cium oxalate came down, which on being filtered out, ignited, and 

 weighed, gave 0.82 per cent, showing that all the calcium had gone 

 into solution. In the filtrate from the calcium oxalate ammonium 

 sulphide gave a black precipitate of ferrous sulphide, which was 

 filtered out, dissolved in hydrochloric acid, and its iron precipitated 

 with ammonium hydroxide and weighed as ferric oxide. A small 

 amount of manganese oxide, determined as 0.07 per cent, was also 

 recovered here. The filtrate, from which iron, manganese, and 

 calcium had now been completely removed, was evaporated to dry- 

 ness three times with concentrated nitric acid to destroy the tartaric 

 acid, and the separated tungsten trioxide dissolved off the dish with 

 ammonium hydroxide, and poured through a filter into a crucible 

 in which it was ignited and weighed as tungsten trioxide. The 

 amount of tungsten trioxide obtained was not sufficient to satisfy 

 all of the bases, but it seemed most probable that it had been united 

 with all of the calcium and part of the iron. 



To determine whether scheelite is soluble in tartaric acid, some clear 

 crystals were broken from a specimen from Zinnwald, powdered, and 



> Quantitative Analysis, translated by W. T. HaU, 3d edition, 1911, p. 296. 



