364 S. L. Penfield—Descloizite from Mexico. ° 
lecting and weighing the water in a chloride of calcium tube 
The air-dry mineral did not lose weight by heating to 100° C., 
and lost only 0°12 per cent by heating for two hours at about 
360° C. 
The results of the analyses are as follows: 
z, | 8 III Mean Ratio. 
V.0; 19°00 18°90 Spa i 18°95 104 
As.0; Le ey oes eee 3°85 3°78 3°82 ‘016 12k 
P,0; Si doe eta ea oe ‘18 Mae ee 4 | “001 
PbO 54°99 54°91 54°89 54:93 247 
CuO 6°76 6°19 66 67 085 484 
O 12°14 12°34 12°23 12°24 151 
FeO ee ee 06 a) ‘0 001 
H,O 245 2°65 272 2°70 1 
ee a ae es Be ll 
99°74 
The ratio of the pentoxide to the protoxide to water = 
121: 484: 150 = 1:400:124=4:16:5. If weassume the 
ratio to be 1:4:1 we obtain the formula R,(VO,),, R(OH), or 
R,(OH)VO, which is now regarded as the true formula for des- 
cloizite. It does not seem probable that the ratio 4: 16:5 giv- 
ing a complicated formula, is correct. The excess of water 1s, 
however, not due to the presence of hygroscopic water, and 
especial care was taken, as explained above in the description 
of the method, to obtain an accurate and sharp determination. 
Unfortunately our knowledge of descloizite is somewhat 
oe but it probably has the formula R,(OH)VO, or 
O 
ov = O, and with our present knowledge I preter to 
R<697 
refer the vanadate, which has been analyzed, to this species, it 
differing only in having a part of the vanadic acid replaced by 
arsenic acid. ; 
As to the purity of the material which was analyzed, I will 
state that the specimens were apparently homogeneous, and two 
thin sections which were prepared revealed no impurity when 
examined with the microscope. 
In regard to the relation between this mineral and Frenzel’s 
tritochorite, little can be said. He states that his mineral, 
have the same density and are alike in many particulars as seeD 
y the following comparison of the analyses. 
