Messrs. F. and E. Rodgers on certain Metallic Cyanurets. 101 



flesh colour, and then dissolves it : the filtered solution is 

 colourless. A small portion of the cyanuret appears to re- 

 main undissolved, even in a large quantity of water. The 

 cyanuret of lead is sparingly soluble in cold water. 



The protocyanurct of copper cannot be conveniently preci- 

 pitated from the acetate by means of hydrocyanic acid. The 

 solution of the acetate becomes turbid, and remains in that 

 state for a considerable time. The acid employed in this expe- 

 riment was that prepared according to the process of Mr. 

 Laming. 



The se&qnicyanuret of chromium, according to Berzelius, has 

 not yet been obtained in an isolated form ; but it seems that it 

 may be prepared by the following process. When a solution 

 of cyanuret of potassium is added to a solution of the double 

 sulphate of chromium and potash, in cold distilled water, an 

 immediate grayish white precipitate is obtained, which falls in 

 distinct masses. The precipitate is broken up by agitation, 

 and then subsides rapidly in the form of a rather dark green 

 powder. On the addition of another portion of cyanuret of 

 potassium, a fresh precipitation takes place. Finally, after all 

 the oxide of chromium is precipitated, the solution evolves the 

 odour of hydrocyanic acid. Owing to the latter fact, and to 

 the precipitate appearing like the hydrated oxide, it might be 

 mistaken for the oxide, and the behaviour of the cyanuret of 

 potassium in the solutions of the oxide of chromium might be 

 compared to that of the sulphuret of potassium. But the pre- 

 cipitate dissolves slowly in distilled water acidulated with nitric 

 acid, and a rather copious precipitate of cyanuret of silver is 

 thrown down on the addition of nitrate of silver to the solu- 

 tion. The experiment, however, was performed on rather 

 small quantities of the materials, and requires, therefore, to be 

 carefully repeated. 



Cyanuret of barium throws down a copious precipitate from 

 the solution of the double sulphate of chromium and potash: 

 the precipitate consists of sulphate of baryta mixed with the 

 supposed cyanuret of chromium. The supernatant solution 

 smells strongly of hydrocyanic acid, especally if the operation 

 is continued after the oxide of chromium is precipitated. 



11. Berzelius describes an hydracid, analogous to the per- 

 salts of iron, which is prepared by decomposing, by dilute sul- 

 phuric acid, the peculiar kind of ferrocyanuret of lead which 

 is generated when the red cyanuret of iron and potassium is 

 added to a solution of a salt of lead. It is, perhaps, the best 

 mode of obtaining it in a perfectly pure form ; but when this 

 is not required, the following process may be employed. The 



