

37 



Action of sulphide of hydrogen upon clay and lime, cold and hot. 



Well-washed sulphide of hydrogen passed into cold slaked lime 

 (obtained from Buxton) in a tube, colours the lime green as soon as 

 it comes into contact with it, and the progress of the gas along the 

 tube corresponds with the coloration. Lead-paper is not affected 

 until the lime becomes coloured close up to the exit. 



The same gas, passed into a tube containing slaked lime kept 

 about 600 Fahr. at the middle, but cool at both ends, acts differ- 

 ently. The cool lime at the inlet end becomes coloured ; the hot 

 lime in the middle remains white, and the cool lime at the exit end 

 becomes coloured, and lead-paper is stained as soon as these two 

 cool portions are saturated, while the middle portion remains un- 

 changed in colour. 



The same gas, passed into a tube containing hot lime only, causes 

 no discoloration, but instantly blackens lead-paper placed at the exit 

 end ; and upon being conducted into a tube of cold lime, colours it as 

 if it had just passed from the vessel in which it is produced. 



The same gas was passed into a tube containing lime which had 

 been thoroughly dried at 600 Fahr., and cooled out of contact with 

 the air. No discoloration of the lime took place, but the gas passed 

 unaffected by the lime, and blackened lead-paper. Water added to 

 the lime gives it the power of decomposing the gas as if it had riot 

 been heated. The presence of more water than is necessary to form 

 hydrate of lime (Ca O, HO), is thus shown to be required for the 

 decomposition of sulphide of hydrogen by slaked lime. 



Sulphide of hydrogen passed into a tube of cold clay is taken up 

 in considerable quantity, and the clay becomes black from the forma- 

 tion of sulphide of iron. The blackening begins at the inlet end, 

 and progresses with the passage of the gas towards the exit end of 

 the tube. 



The same gas, passed into clay, heated to 500 or 600 Fahr., 

 gives the same reactions ; but when the clay has been heated and 

 well-dried, and cooled in the closed tube, it takes up a very small 

 quantity of the gas. 



Coal-gas, quite free from sulphide of hydrogen, when passed 

 through hot lime, blackens lead-paper, showing that masked and 

 hitherto irremoveable compounds have been so- altered as to be easily 

 removeable. The lime does not take up sulphide of hydrogen, but 



