178 



ESSAY XIII. 



SECTION II. 



(a) Corrosive sublimate had likewise no effect upon 

 plumbago when they were subjected to sublimation together. 

 (&) With sal ammoniac by the same operation, I obtained 

 flores martiales and a little caustic volatile alkali. The 

 remainder was unchanged, (c) When I mixed plumbago 

 with a double quantity of sulphur, and again separated it 

 by sublimation, I found the weight of the plumbago to be 

 the same as before, (d) Upon fusing it with four parts 

 of vitriolated vegetable alkali in a covered crucible, I obtained 

 hepar sulphuris. (e) When one part was exposed to the 

 action of heat with eight parts of litharge in a close crucible, 

 the calx of lead was reduced ; but no reduction followed 

 when it was treated with glass of antimony. That the calx 

 of lead acts more powerfully upon phlogiston than the calx 

 of antimony, appears upon mixing and fusing litharge with 

 regulus of antimony ; for by this means regulus of lead 

 and black glass of antimony are obtained. (/) By distilla- 

 tion with common salt none of the acid was expelled, (g) 

 On distillation with nitre no detonation took place in the 

 retort. 



SECTION III. 



(a) I put 2 drins. of levigated plumbago, together with 

 1 oz. of purified nitre, into a red hot crucible. At first a 

 strong effervescence and afterwards a violent detonation 

 took place. There remained in the crucible a black shining 

 liquid matter, which still contained a great deal of plumbago. 

 (&) I then mixed one part of levigated plumbago with six 

 parts of nitre, and the same detonation followed. The mass 

 remaining in the crucible was exactly the same as the 



