New Substance discovered in Davidsonite. 431 



8. Arseniate of soda — white flocky precipitate. 



9. Sulphate of soda — no precipitate. 



10. Chromate of potash — copious yellow precipitate. 



11. Tartrate of potash — slight white precipitate. 



12. Infusion of nutgalls — no precipitate. 



B. The caustic soda solution was mixed with a solution 

 of carbonate of potash, and sulphuric acid added in slight. 

 excess. When this solution was sufficiently concentrated 

 by evaporation, it was set aside to crystallize. After stand- 

 ing twelve hours, a copious deposition of crystals was ob- 

 served. These consisted in a great measure of large prisms 

 of sulphate of soda; but with these a number of small 

 octahedrons were mixed, some of which had the edges and 

 terminal angles truncated, while others Avere quite entire. 

 The whole was set aside in a dry place, till the crystals of 

 sulphate of soda had effloresced, and fallen to powder, 

 after which the octahedrons were easily separated. 



From experiments made with them the following cha- 

 racers were deduced : 



They dissolve easily in water. 



They do not effloresce when exposed to the air. 



When heated they undergo the aqueous fusion, swell up 

 and become white and opaque. 



Their taste is sweet and astringent. 



In a solution of these crystals, chloride of barium pro- 

 duces a copious white precipitate, insoluble in excess of acid. 



Caustic ammonia produces in the solution a white pre- 

 cipitate, which is immediately dissolved in excess of the 

 precipitant. 



Chloride of platinum causes a heavy yellow precipitate. 



This salt is therefore composed of sulphuric acid, white 

 substance, potash and water. 



C. A portion of the reddish brown matter, which re- 

 mained undissolved in caustic soda, was dissolved in muria- 

 tic acid, and caustic ammonia added. A white precipitate 

 appeared, which was immediately dissolved, when the am- 

 monia was added in excess. There could be no doubt, 

 therefore, that this substance was the same in its nature as 

 the former. It was cautiously dried on the sand bath. 

 When dry, it had a buff colour, which appeared to be 

 slightly deepened, when it was heated to redness. The 



