1835.] onDysluite. 287 



weighed 2 grains ; dried by the blow-pipe, it melted with 

 effervescence into a transparent colourless glass with 

 carbonate of soda, and was not soluble in acids. It was, 

 therefore, silica. 



4. The liquid which had passed through the filter, to- 

 gether with the washings, was evaporated down to a 

 manageable quantity. It was then neutralized and pre- 

 cipitated by caustic ammonia, added in excess. The whole 

 was thrown on a filter, and the yellowish red residue on 

 the filter well washed. The colourless liquid which passed 

 through the filter was concentrated on the sand-bath, 

 partly to drive off the excess of ammonia, and partly to 

 reduce it to a manageable quantity ; during the concentra- 

 tion white flocks fell. The quantity of this precipitate was 

 much increased on adding carbonate of soda to the liquid. 



This precipitate was collected on a filter, washed and 

 dried. It possessed the following properties : 



Q..) When heated to redness, it became yellow, but re- 

 sumed its white colour on cooling. 



(2.) Soluble in sulphuric, nitric and muriatic acids. The 

 solutions colourless ; and when neutral, possessed the 

 peculiar taste which characterizes the salts of zinc. 



(3.) The nitric acid solution precipitated in white flocks by 

 caustic ammonia, re-dissolved by an excess of the precipitant. 



(4.) Precipitated in white flocks by caustic potash, and 

 re-dissolved by an excess of the precipitant. 



(5.) Precipitated in white flocks by the alkaline carbo- 

 nates, and not re-dissolved by an excess of the precipitant. 



(6.) The sulphuric acid solution being cautiously evapo- 

 rated, yielded transparent white crystals in four-sided 

 prisms, almost rectangular, and easily recognizeable as sul- 

 phate of zinc. 



It is obvious that the powder thus obtained was oxide of 

 zinc. 



To the liquid from which this precipitate had been ob- 

 tained, oxalate of ammonia was added, and the liquid con- 

 centrated. In this way an additional precipitate was slowly 

 obtained, which was oxalate of zinc. 



All these precipitates being collected and exposed to a 

 strong red heat, left 16*8 grains of oxide of zinc. 



5. The red precipitate collected on the filter, (in para- 

 graph 4) was well washed, and while still moist, was dis- 



