518 Hidden and Warren — Yttrocrasite. 



of the oxides. Iron was separated from the uranium of this por- 

 tion by passing hydrogen sulphide through the warm solution 

 when nearly saturated with ammonium carbonate.* 



The filtrate from the original hydrofluoric acid treatment 

 was evaporated to fuming with sulphuric acid. After cooling 

 and dilution with water, ammonium hydroxide and freshly 

 prepared colorless ammonium sulphide were added and the pre- 

 cipitated hydroxides were digested on the water-bath. After 

 filtration and solution the precipitation and digestion were 

 repeated and the tungsten thus extracted was determined 

 in the combined filtrates. Tin was tested for, but not found. 

 Doubtless a little tungsten remains with the titanium, etc., but 

 in the writer's experience the above method involves smaller 

 errors than the one where a sodium-carbonate-sulphur fusion is 

 made. After the second digestion with ammonium sulphide 

 the precipitated hydroxides were allowed to stand with strong 

 sulphurous acid, whereby the dark colored iron sulphide and 

 some titanium and uranium passed into solution. The 

 hydroxides were again dissolved in hydrofluoric acid, and 

 later expelled with sulphuric acid, and the solution barely 

 neutralized with ammonium hydroxide, after which an excess 

 of ammonium carbonate was added, together with some fresh 

 colorless ammonium sulphide. By this means the uranium 

 was extracted together with a little titanium. By repeated 

 reprecipitations in the presence of ammonium carbonate, the 

 uranium was obtained free from all but a trace of iron and 

 titanium. A little additional iron was recovered from the 

 main precipitate by means of sulphurous acid. The small 

 amount of titanium which goes with the iron is easily recov- 

 ered by precipitation with sodium acetate in the presence of 

 acetic and sulphurous acids. 



The ignited oxides of titanium and niobium when fused 

 with acid potassium sulphate and leached out with cold water, 

 pass almost completely into solution (all but 0*0021 gr. from 

 0"3139 q;i\ in the sample treated). Qualitative tests according 

 to the procedure recommended by Dr. A. A. Noyesf showed 

 the presence of enough niobium to give the characteristic 

 brown color to the solution after reduction by means of a zinc 

 column, and to produce immediately an abundant white per- 

 cipitate in the solution of mercuric chloride. This test is a 

 delicate one and the reaction may be obtained' with only a few 

 milligrams of niobic acid. This taken in connection with the 

 fact that but a small residue remains from the leaching of the 

 bisulphate fusion, points to the presence of only a small 



* For suggesting this satisfactory form of the iron-uranium separation we 

 are indebted to Dr. B. B. Boltwood of New Haven. 



f A System of Qualitative Analysis, Technology Quarterly, vol. xvii, No. 3, 

 1904. 



