CALIFORNIA ACADEMY OF SCIENCES. 41 



and ignited in a muffle at a bright red until it ceased to lose 



weight. The results were as follows: 



a b 



Pt. cru. -f- CaO + filter ash 24.789' 24.7S9 4 



" 24.517 ;> 24.516s 



CaO .272 .2729 



Two more indej^endent determinations, in which the oxalate 

 was ignited to carbonate, gave results as follows: 



c d 



CaC0 3 + Pt. cru. + filter ash 25.099 e 25.096 4 



24.615 5 24.611' 



CaC0 3 .484i .484 s 



Equivalent resjjectively to CaO .271 and .271o. 



Two independent determinations as sulphate made by treating 

 one gram of the powdered mineral with 5 c. c. pure hydrofluoric 

 acid and 5 c. c. pure sulphuric acid, evaporating cautiously to 

 dryness and igniting at a dull red heat in a weighed platinum 

 crucible, gave the following results: 



CaS0 4 .658 6 .659* 



Equivalent respectively to CaO .271= .2717. 



The mineral therefore contains somewhat over 27% lime. 



Taking the average of the experimental results and calling the 

 remainder anhydrous boracic acid, we have the following for the 

 percentage composition of the mineral: 



Lime (CaO) 27.175 



Anhydrous boracic acid (B. 2 3 ) [50.990] 

 Water (H 2 0) 21.835 



100.000 



