94 Dr. Thomas Thomson on the 



1. When a quantity of the saline matter is mixed with 

 water in a retort, a strong effervescence takes place, and 

 nitrous gas escapes in torrents. The whole dissolves in the 

 water, with the exception of a small quantity of white mat- 

 ter, the weight of which varies in different specimens. This 

 white matter when dried is a tasteless powder, insoluble in 

 water. When heated it takes fi^e, and burns with a blue 

 flame, while some sulphur sublimes. What remains is 

 pure sulphate of lead. These phenomena characterize sul- 

 phite of lead. Hence, it is evident, that the saline matter 

 from the leaden chambers contains sulphite of lead. From 

 550 grains of saline matter I obtained 8-43 grains of sul- 

 phite of lead, or about 1*53 per cent. In another experi- 

 ment 160 grains of the saline matter yielded 1*4 grains of 

 sulphite of lead, or somewhat under one per cent. These 

 two experiments show the two extremes; in all the others 

 the quantity was intermediate. 



2. 58 grains of the saline matter were heated in a small 

 retort. The solid matter became partially liquid and fumes 

 of nitrous acid made their appearance. On increasing the 

 heat an effervescence took place, and gas passed rapidly. 

 It was yellow like nitric acid fumes, and like that acid 

 acted on mercury, which prevented me from collecting 

 the gas. When the effervescence stopped, a colourless 

 liquid remained with a small deposit of sulphite of lead at 

 the bottom of the retort. This liquid was colourless, but it 

 effervesced violently giving out nitrous fumes when mixed 

 with water. It remained, therefore, the same mixture or 

 compound as the original saline matter. 



3. When the saline matter is triturated with carbonate 

 of ammonia, combination takes place without any sensible 

 decomposition. 



4. It was triturated with a quantity of bi-carbonate of 

 potash in powder, which from previous experiments was 

 judged capable of just saturating the uncombined acids. 

 Fumes of nitric acid were given off till the whole became 

 quite dry. The trituration being continued the mixture 

 softened into a white paste, which was left exposed to the 

 air for some hours. On examining this residue, it was 

 found to consist chiefly of a mixture of sulphate of potash 

 and carbonate of potash with a very little nitrate; the nitric 

 acid had been almost all dissipated during the trituration. 



