Harrington — Interesting Variety of Fetid Calcite. 347 



reactions with salts of silver, lead, cadmium, etc. If, again, the 

 calcite be gently heated in a test-tube, hydrogen sulphide is 

 liberated, and on heating somewhat more strongly the mineral 

 generally decrepitates and gives off more hydrogen sulphide. 

 On heating to 160° C. it shows a strong, deep yellow phos- 

 phorescence which persists for several minutes after removal 

 from the source of heat. 



From what has been stated it is evident that the hydrogen 

 sulphide is the cause of the odor evolved when the calcite is 

 scratched or rubbed, and although the quantity seems small 

 when stated as percentage by weight it amounts to about 500 

 cubic inches of the gas per cubic foot of the mineral. Per 

 cubic yard this would be about 13,500 cubic inches (a barrel 

 and a half) of the gas, and the total quantity bottled up in the 

 limestone of the region must be exceedingly large. It may 

 exist in the calcite in a liquid condition, as in the case of the 

 liquid carbon dioxide so frequently present in quartz, or in 

 conjunction with water, or even with carbon dioxide. Mr. 

 Douglas Mcintosh, M.Sc, lecturer in chemistry, has kindly 

 made some experiments for me which are interesting in this 

 connection. He found that if solid carbon dioxide be dropped 

 into liquid hydrogen sulphide and the tube sealed, as the tem- 

 perature rises to that of the room the carbon dioxide dissolves 

 and a homogeneous liquid is obtained, giving no evidence so far 

 as appearance is concerned of the presence of two distinct 

 compounds. 



A small quantity of distilled water, again, was put into a 

 tube and frozen, an equal volume of liquid hydrogen sulphide 

 added and the tube sealed. When the ice melted, the two 

 liquids could be seen to be separated by a distinct film — pos- 

 sibly of sulphur — which prevented their intermixing. In most 

 cases when the tubes were heated they burst before the tem- 

 perature reached 100° C. The same was also true if the tubes 

 were inverted in position, that is with the water above the 

 hydrogen sulphide ; after standing for a short time the film 

 gave way and the tube burst, possibly because of some sudden 

 reaction between the two liquids. In one case, however, a tube 

 which showed the distinct film separating the two liquids was 

 forgotten and allowed to stand for some weeks. The film had 

 then disappeared and, so far as one could tell by the eye, the 

 two liquids had completely intermixed. On cooling the tube 

 until the water crystallized out and then allowing it to gradually 

 attain the temperature of the room, no separation of the two 

 liquids took place. This would indicate that under the condi- 

 tions of pressure in the tube, mutual solution of the water and 

 hydrogen sulphide had taken place, and similar conditions may 

 exist in the case of the fluid-cavities of the calcite. 



