346 Harrington — Interesting Variety of Fetid Calcite. 



that Hunt worked with the finely pulverized mineral, from 

 which most of the hydrogen sulphide had been liberated, or 

 that the gases were not passed into the solutions of the salts in 

 question for a sufficient length of time. 



A specimen of the calcite was found to have a specific 

 gravity of 2*713 and gave on analysis the following percentage 

 composition : 



Lime _ 55-330 



Magnesia 0*540 



Ferric oxide _ tr 



Carbon dioxide __ 43*925 



Sulphur as H 2 S 0-016 



Phosphoric anhydride . tr 



Insoluble matter _ 0*026 



99*837 



The sulphur was determined by dissolving the mineral in 

 dilute hydrochloric acid, passing the evolved gases into an 

 alkaline solution of cadmium chloride and weighing the pre- 

 cipitate of cadmium sulphide. In the estimation of the 

 phosphoric anhydride the mineral was dissolved in nitro- 

 hydrochloric acid, so that if any phosphorus were present as 

 phosphide its oxidation to orthophosphate might be ensured. 

 As the quantity of insoluble matter was insignificant, the deter- 

 mination was made upon about thirty grams of mineral — 

 hydrochloric acid being the solvent. The filtrate from the 

 insoluble matter was tested for sulphates, but gave no precipi- 

 tate with barium chloride. In the analysis of another speci- 

 men of the calcite Mr. Lodge obtained results very similar to 

 the above, but found a slightly higher percentage of hydrogen 

 sulphide (0*021). 



The following figures illustrate the different results obtained 

 in determinations of the hydrogen sulphide according to the 

 coarseness or fineness of the calcite : 



Powder of Very- 



Lumps, medium fine 



fineness. powder. 



H 2 S from 29'45 [ __ 0*00471 0*00176 0*00035 



grams or mineral \ 



Percentage of H a S 0*01600 0*00560 0*00120 



The figures show that the fine powder contained less than 

 yig-th of the amount present in the unpulverized material, and 

 had the grinding been further prolonged there would no doubt 

 have been a still greater difference. 



On grinding a few fragments of the calcite under water in a 

 porcelain mortar and filtering, the water contains sufficient 

 hydrogen sulphide in solution to give the appropriate color 



