674 Ford and Bradley — Footeite and Connellite. 



determine the amount of N 2 5 present only by the phenol 

 disulphonic acid or Sprengel's method. This is a delicate and 

 accurate colorimetric method used commonly in water analyses 

 and there is no doubt as to the substantial accuracy of the 

 determinations made by it. The authors' thanks are due to 

 Prof. G. S. Jamieson of the chemical department of the 

 Sheffield Scientific School for assistance in making these deter- 

 minations. The water determinations quoted were made by 

 heating the mineral mixed with lead chromate in closed 

 glass tubes and passing the vapors given off through layers of 

 hot copper filings and lead chromate. The water collected in 

 the upper portion of the tube was then weighed directly. It 

 was found difficult to control this operation so as to insure the 

 absolutely neutral character of the water collected. In the 

 case of the determination given in the analysis of the connellite 

 from the Tintic district the water was perfectly neutral, but in 

 the case of the analysis of the Bisbee material it still showed a 

 slight acid reaction. It is thought probable, however, that any 

 increase of weight due to the presence of the small amount of 

 an acid radical would be fully compensated by other errors of 

 the method and that the values given represent fairly accu- 

 rately the amount of water present. It is to be regretted that 

 the amount of material available for analysis was so small as to 

 preclude the use of other methods. 



Below are given the following analyses : I, The original 

 footeite by Koenig ;* II, Connellite from Cornwall by Pen- 

 field ; f III, Connellite from the Czar mine, Bisbee, Arizona, 

 by Bradley ; IY, Connellite from the Grand Central mine, 

 Tintic District, Utah, by Bradley ; Y, Theoretical composition 

 according to the proposed new formula : 





I 



II 



III 



IV 



V 



CuO 



... 71-6 



72-3 



73-38 



73-41 



73-98 



CI 



._. 5-6 



7'4 



6'82 



7-05 



6-93 



so 3 





4-9 



3-15 



3-84 



3-92 



N 2 O b 







0-72 



0-30 





HO 





16'8 



17-13 

 101-20 



16-81 

 101-41 



16-73 



2 ^ 







Total 



101*8 



101-56 



= C1 ... 





1-7 



1-53 



1-59 



1-56 



100-1 99-67 99-82 100-00 



Discussion of Analyses. — The above analyses show a sub- 

 stantial agreement in the percentages of the different radicals. 

 They present, however, some difficulties when the attempt is 

 made to interpret them and to derive from them a satisfactory 



*Loc. cit. t Tnis Journal, xl, 82, 1890. 



