1836.] Analysis of the residuum of fired gunpowder. 3 



11. — The precipitate last mentioned was collected, washed, 

 and dried ; and was compared with the weight of the preci- 

 pitate obtained from an experiment made with a similar quan- 

 tity of the residuum, only treated with cold water, and not 

 boiled. The quantity of sulphuret of silver (i. e. the preci- 

 pitate) obtained in the experiment by boiling was grains 12 ; 

 the quantity in the other case was grains 27. 



12. — These last two steps in the examination point out the 

 presence of sulphur in combination with hydrogen, and with 

 potassa ; or sulphuretted hydrogen, and hydro-sulphuret of 

 potassa. 



13 — Solution of soap in alcohol gave no discoloration. 



14. — After removing the sulphuric and carbonic acids, and 

 the sulphur from a portion of the solution, it was evaporated 

 to dryness. From the course pursued there should result 

 saltpetre, being potassa, the base shown by the tartaric acid 

 (7) in combination with the nitric acid of the tests. The 

 salt collected resulted accordingly ; it was nitre, and defla- 

 grated as nitre does when thrown on red hot charcoal. 



15. — -There appeared to be a small quantity of uncombined 

 alkali ; for after precipitating the sulphuric and carbonic 

 acids by nitrate of baryta, the clear solution changed red- 

 dened litmus paper blue ; merely a drop or two of nitric acid 

 however neutralized as much alkali as resulted from 100 

 grains of the original substance. After this neutralization, 

 and after precipitating the sulphur by the nitrate of silver, the 

 solution contained free acid which was indicated by turning 

 blue litmus paper red : this proceeded from the nitrate of 

 silver, for the silver combining with the sulphur, set the nitric 

 acid free, the alkali of the solution being previously neutra- 

 lized. This acid manifested itself and was driven off in yel- 

 low fumes in melting the saltpetre. 



16. — The insoluble residue retained by the filter (5) was 

 small ; it was black, but viewed by the microscope, it con- 

 tained numerous white specks which appeared to be earthy 

 matter. It burned quietly on red hot charcoal before the 

 blow-pipe, without the smell of sulphur, and changed its co- 

 lour from black to brown. The earthy matter partially dis- 

 solved with effervescence in nitric acid. I consider this resi- 



