264 JEakle and Rogers — WUkeite, a New Mineral. 



gravity, determined with 1*6 gms. of material by means of the 

 py knometer, is 3'234 ; at. 20°" 0. 



The index of refraction is 1/640 ± '005, determined by the 

 Becke test with reference to liquids of known index of refrac- 

 tion. The double refraction is about "004, determined from 

 the thickness of a thin section by observing the maximum 

 interference color of diopside. The sections give gray and 

 white interference colors of the first order. Basal cleavage 

 plates show a negative uniaxial figure. The elongation of 

 prismatic sections in a slide is parallel to the faster ray. The 

 physical properties as a whole are like those of apatite. 



Chemical Properties. — Wilkeite when intensely heated 

 becomes colorless and then assumes a pale bluish green color 

 on cooling. It fuses on its very thin edges, but the fusibility 

 is above 5. It is easily soluble in dilute hydrochloric and 

 nitric acids, leaving flocculent silica, but most of the silica is 

 soluble and can only be removed by complete evaporation. 

 In large fragments or grains gelatinous balls with white 

 opaque centers and translucent exteriors are formed by the 

 acids. In nitric acid, heated nearly to the boiling point, a 

 distinct effervescence is obtained. That the evolved gas is 

 C0 2 was proved by leading it into clear barium hydroxide 

 solution. The wilkeite gives strong reactions for calcium and 

 for the phosphate and sulphate radicals. No test for fluorine 

 or chlorine was obtained. The mineral is practically anhy- 

 drous, as hardly more than a trace of water was obtained by 

 heating the powdered mineral in a tube by the Penfield 

 method. 



Several analyses of the mineral were made by different 

 methods and with different samples. The results showed that 

 the constituents were constant in amount. The silica was 

 always first removed by two complete evaporations and the 

 amount determined by subsequent treatment with HF and 

 H„S0 4 . The sulphate was determined as BaS0 4 , and also 

 as CaS0 4 by direct precipitation from a slightly acid solution 

 by means of alcohol. The results by alcohol were slightly 

 lower than those obtained with BaCl 2 or Ba(N0 3 ) 2 . 



The calcium was determined in three ways : 1. Indirectly, 

 by successive precipitations as CaS0 4 , Ca 3 P 2 O s and CaC 2 4 - 

 2H 2 and combining the calculated amounts of CaO. 2. Directly 

 by precipitation as CaS0 4 by means of H„S0 4 and alcohol.' 

 3. Directly, by addition of ammonia and then acetic acid to 

 redissolve the calcium phosphate and precipitation as calcium 

 oxalate, this method giving the most accurate results. In the 

 determination of the phosphate considerable difficulty was 

 encountered in getting a complete precipitation by the ordinary 

 molybdate method or by the Woy method, and it was found 



