42 HILLEBRAND, MERWIN AND WRIGHT. [April 25, 



what the drawing of conclusions as to the formulas assignable to 

 the vanadates, since we know nothing positive as to its chemical con- 

 dition and whether foreign to the vanadate molecule or a part of it, 

 nor, if foreign what part if any of the water is to be assigned to it. 

 So much may, however, be affirmed with positiveness from careful 

 microscopical examination, that the sample of hewettite analyzed 

 represents essentially a single homogeneous mineral and not a 

 mechanical mixture of different minerals. This belief is supported 

 by the behavior of the mineral when it is gradually brought into 

 complete solution by successive treatments with much hot water, 

 for the solution of the molybdenum keeps pace with that of the 

 vanadium. The molybdenum may perhaps best be considered as 

 forming' calcium molybdate which is held in solid solution. This 

 assumption has been made because it seems called for by the vary- 

 ing proportions of molybdenum in different specimens and by the 

 difficulty of deducing a probable formula under any other assumption. 

 Other Constituents. — The absence of any acidic constituent in 

 hewettite to offset the sodium forces us to group this with the 

 calcium as part of the vanadate molecule, unless perchance there be 

 an admixture of a vanadyl-vanadate (see p. 41). In metahewettite 

 the potassium may be referred with a high degree of probability to 

 the silicate of which mention has been made. This silicate requires 

 a small part of the water. There is no evidence of such a silicate in 

 the Peruvian mineral. The sodium and magnesium of metahewet- 

 tite are not accounted for, but in part at least may belong to the 

 silicate mentioned or to another, except in so far as the chlorine 

 present in small amount may claim some of the sodium (also in 

 hewettite). The amounts reported for sodium may be subject to 

 considerable error in both analyses, and if in error are too high. 

 The iron oxide is no doubt admixed. 



After deducting M0O3 and its equivalent of CaO and neglecting 

 V2O4, V2O3 and all other minor constituents except NaaO in I., the 

 molecular ratios deducible with employment of the 1913 atomic 

 weights are : 



I. II. 



V2O3 306 3.00 



CaO i.oo 1. 00 



H2O 9.61 9.20 



