on the Nature of certain Bodies. 487 



ments performed in vacuo, is owing to the small quantity 

 of moisture furnished by the hydrogen gas introduced, and 

 that the fusible substance, heated out of the piesence of 

 moisture, is incapable of producing volatile alkali. 



MM. Gay Lussac and Thenard, it is stated, after having 

 obtained three fifths of the ammonia or its elements that had 

 disappeared in their experiment, by heating the product, 

 procured the remaining two fifths, by adding water to the 

 residuum, which after this operation was found to be potash. 

 No notice is taken of the properties of this residuum, which, 

 as the details seem to relate to a single experiment, probably 

 was not examined ; nor, as moisture was present at the be- 

 ginning of their operations, could any accurate knowledge of 

 its nature have been gained. 



I have made the residuum of the fusible substance after 

 it has been exposed to a dull red heat, out of the contact of 

 moisture, an object of particular study, and I shall detail its 

 general properties. 



It was examined under naphtha, as it is instantly de* 

 stroyed by the contact of air. 



1. Its colour is black, and its lustre not much inferior to 

 that of plumbago. 



2. It is opaque even in the thinnest films. 



3. It is very brittle, and affords a deep gray powder. 



4. It is a conductor of electricity. 



5. It does not fuse at a low red heat, and when raised to 

 this temperature, in contact with plate glass, it blackens the 

 glass, and a grayish sublimate rises from it, which likewise 

 blackens the glass. 



6. When exposed to air at common temperatures, it usually 

 takes fire immediately, and burns with a deep red light. 



7. When it is acted upon by water, it heats, effervesces 

 most violently, and evolves volatile alkali, leaving behind 

 nothing but potash. When the process is conducted under 

 water, a little inflammable gas is found to be generated. A 

 residuum of eight grains giving in all cases about ^o of a 

 cubical inch. 



8. It has no action upon quicksilver. 



9. It combines with sulphur and phosphorus by heat, 



H h 4 without 



