306 W. P. Headden — Some Phosphorescent CalciUs. 



washed out of the oxalate precipitate, so that the boiling wash 

 water will neither yield any crystals on cooling or give a pre- 

 cipitate with ammonia, even after concentration, though there 

 is still yttrium in the precipitate. I have been compelled to 

 postpone the further investigation of this precipitate until I 

 may be able to command more material and greater resources 

 than I have at the present time. 



The presence of an oxide which is precipitated by ammonia 

 in the presence of tartaric acid, and which is precipitated by 

 oxalic acid from a solution containing free hydrochloric acid, 

 but not by a saturated solution of potassic or sodic sulphate, is 

 taken as conclusive proof of the presence of yttria. The 

 characteristic absorption spectrum of erbia is relied upon as 

 establishing its presence, but the question of the presence of 

 the other members of the group is held in abeyance. 



We have not as yet gained even a hint in regard to the cause 

 of this property of the yellow calcite, i. e. of phosphorescing 

 after insolation. I have not met with any statement which 

 would lead one to infer that the presence of zinc or of any 

 member of the yttrium or cerium group in the form of carbon- 

 ate would impart this property to the calcium salt. The salts of 

 the rare earths, the ignited yttria sulphate excepted, seem to 

 show phosphorescence in a weak and rather unsatisfactory 

 degree even when exposed to the action of the cathode ray in a 

 radiant matter tube. When calcium is present the deportment 

 of yttria and samaria is radically changed, especially in regard 

 to the phosphorescent spectrum that they give. Some such fact 

 may obtain in this case of phosphorescence after insolation. 



A very large amount of work was done of which no record 

 appears in this article, but the results of which serve as the 

 basis for the following statements ; the total amount of rare 

 earths may be greater in a non-phosphorescent than in a phos- 

 phorescent calcite ; the oxides of the yttria group are relatively 

 more abundant in the phosphorescent than in the non-phos- 

 phorescent ; the white, opaque calcite contains less zinc oxide 

 and a much smaller amount of the rare earths than the yellow, 

 phosphorescent portions. 



Th& second of these statements is illustrated by the ratios 

 found for the yttrium and cerium groups in the following four 

 instances ; in a sample of yellow, strongly phosphorescent 

 calcite the ratio of the yttrium to the cerium oxides was \\ : 1, 

 in another sample -of yellow calcite this ratio was 1 : 1, but in 

 two samples of feebly or non-phosphorescent material this 

 ratio was 1 : 2*4 and 1 : 2*6 I'espectively. The weight of calcite 

 used in making these determinations was 500 grams in each case. 



The white, opaque cleavage pieces, obtained by breaking up 

 crystals of dog-tooth spar, have in no instance been observed 



