NO. 48. — 1897.] GEOLOGY AND MINERALOGY. 



69 



The following analyses of dust plumbago, also by Cochran, 

 in which the carbon is estimated b^ the loss of weight when 

 the mineral is burned in oxygen gas, show an inferiority in 

 the samples in point of percentage of carbon to those already 

 quoted : — 





Per cent. 



Loss on ignition in air 

 Ash 



Graphitic carbon 



3-1 

 22-4 

 74-5 



2-2 

 22-6 

 74-8 



3-5 

 28-4 

 68-1 



1-8 

 16-2 

 82-0 





100-0 



100-0 



100-0 



100-0 



Sulphur 



0-17 



0-07 



0-22 



0-45 



The following analyses made by Cochran of plumbago 

 dust exhibit the percentage of iron as well as the other 

 ingredients : — 



Loss on ignition in air 



1-7 



1-00 



1-5 



2-10 



0-95 



1-35 



1-5 



Ash ... 



6-0 



5-00 



17-8 



7-60 



7-00 



8-60 



17-8 



Graphitic carbon .. 



92-3 



94-00 



80-7 



90-30 



92-05 



90-05 



80-7 





100-0 



100-00 



100-0 



100-00 



100-00 



100-00 



100-0 



Iron ... 



0-22 



0-74 



1-01 



1-08 



1-340 



2-33 



2-66 



Sulphur 



0-05 



0-01 



trace 



0-77 



•014 



0-49 



0-51 



Mr. Ph. Freudenberg adds the following analyses : — 



Loss on ignition in air 

 Ash... 



Graphitic carbon 



Iron... 

 Sulphur 



2-65 



1-90 



0-90 



2-45 



3-87 



12-00 



7-80 



4-80 



34-00 



10-00 



85-35 



90-30 



94-30 



63-55 



86-13 



100-00 



100-00 



100-00 



100-00 



100-00 



3-52 



2-45 



0-47 



4-56 



5-17 



0-32 



2-22 



0-24 



0-09 



3-98 



