i9°5-] 



HALL AND SMITH— COLUMBIUM. 183 



this precipitate gave no reduction test when treated with acid and 

 zinc, nor was anything obtained from it after having added dilute 

 sulphuric acid and a slight excess of ammonium hydroxide. It was 

 free from earthy bases and metallic acids. 



The crystals of the sodium salt (2.5 grams), obtained as outlined 

 in the last paragraph, dissolved almost completely in 20 parts of 

 boiling water and separated in well-defined forms from the cold 

 solution. A portion of this salt heated in a salt of phosphorus bead 

 imparted a blue color to the latter in the reducing flame. 



The next step was to decompose the solution of this crystalline 

 sodium salt with dilute sulphuric acid. The solution was hot. The 

 precipitate which separated was thrown upon a filter and washed, 

 after which it was dissolved in hydrofluoric acid and an equivalent 

 amount of potassium carbonate added in order to form potassium 

 columbium oxyfluoride. The solution was evaporated to dryness 

 upon a water bath, the residue repeatedly moistened, and evapora- 

 tion to dryness repeated until the odor of hydrofluoric acid could 

 not be detected by the smell ; then the salt was baked, taken up in 

 water, and the solution boiled for some time. A trace of tantalum 

 oxyfluoride separated. It was filtered out. On evaporation to 

 crystallization the leafy, characteristic crystals of potassium colum- 

 bium oxyfluoride appeared. They were dried between bibulous 

 paper and then analyzed. 



Analysis : 



0.5502 gram of salt gave 0.2452 gram of oxide and 



0.3224 gram of potassium sulphate 

 0.2452 : 0.3224 :: x/2 : 174 x = 264.6. 



Calculated 



K 2 CbOF 5 H,0. Found. 



Oxide 44-52 44-56 



K 2 S0 4 57.81 58.60 



A portion of crystals No. 4 (page 182) was recrystallized and 

 analyzed. 



0.5588 gram of sample gave 0.2407 gram of oxide and 



0.3232 gram of potassium sulphate 

 0.2407 : 0.3232 :: x/2 : 174 #=259.2. 



Calculated 

 K 2 tbF 7 . Found. 



Oxide 43-93 43-° 8 



K 2 SO, 57.05 57-84 



