522 C. JEL. Warren — Niobium and Tantalum. 



Nb 3 6 Ta 2 5 TiO a 



Taken, *3357 gr. -2246 gr. -0687 gr. 



Found, -3314 gr. -2289 gr. -0667 gr. 



The agreement here is quite satisfactory but as the relative 

 amount of titanic oxide is small, and as the writer had never 

 had any experience with the method, it was decided to make a 

 trial of the method before nsing it in an analysis. In experi- 

 ments 1-4 of those given below Mr. Osborne's directions were 

 followed closely. In Nos. 5 and 6 the time of reduction was 

 increased and in No. 6 the volume of acid was doubled. One 

 other experiment was tried and the temperature raised to 

 nearly 100° C. : but as a separation of the metallic acids took 

 place this one is not included. The results obtained by reduc- 

 tion and titration are as follows ; 



Gram Dif • 



Wgt. taken in grams KMn0 4 Grams ferences 



Time of Vol- , * s re- KMn0 4 in 



No. reduct'n Temp, ume Nb 2 5 Ta 2 B Ti0 2 quired used grams 



1 jhr. 80° C. 50 cc -2163 '1649 



2 " " " -2034 -1062 



3 " " " -2067 '1090 



4 " " " -2283 -1054 



5 1" " " -1889 



6 1" " 10G CC -2140 



2453 -1988 '1450 --•0540 



2083 -1783 -1551 —'0232 



0708 -1254 '1138 -'0116 



2079 '1899 -1630 —'0269 



1933 '1565 '1317 — *0248 



2033 -1814 -1620 —'0183 



The large size and irregularity of the resulting errors led the 

 writer to abandon further work on the method with the con- 

 clusion that it is wholly unsatisfactory as it stands. One source 

 of error in the method is possibly the loss of some volatile, me- 

 tallic fluoride during the removal of the hydrofluoric acid on the 

 water bath. The addition of sulphuric acid with the hydro- 

 chloric in order to prevent such volatilization is inadvisable, 

 since, as Mr. Osborne states, the reduction of the niobium is 

 then far from constant, and it may be added, the tendency of 

 the metallic acids to precipitate dnring reduction would be 

 greater. 



There appears to be, so far as the writer can discover, no 

 method by which more than a rough approximation toward a 

 quantitative separation of these elements can be effected notwith- 

 standing the numerous analyses purporting to have accomplished 

 a separation of sufficient accuracy to warrant considerable 

 speculation as to the chemical constitution of the group of min- 

 erals containing these elements. The problem of their separa- 

 tion is an - extremely interesting one mineralogically as well as 

 chemically, since the constitution of so many highly inter- 

 esting minerals depend on its successful solution. The increas- 

 ing use of tantalum in lamps and perhaps in other ways, and 

 its common occurrence with niobium and titanium make a sat- 

 isfactory quantitative separation of these elements highly desir- 

 able, and it is to be hoped that it may soon be realized. 



Laboratory of Mineralogy, 

 Massachusetts Institute of Technology, Boston, Mass. 



