i32 Mr. H. J. Brooke and Dr. Percy on Percylitef 



His analysis is detailed in the following notice; and I am 

 happy in the opportunity thus afforded me, by calling the 

 mineral Percylite, of permanently associating his name with 

 the science of mineralogy, to which his chemical labours have 

 already contributed so much valuable assistance. 



H. J. B. 



Chemical Examination of the Blue Crystals. 

 By John Percy, M,D., F.R.S. 



1. By slight heat the blue colour changes to emerald-green, 

 and reappears on cooling. 



2. Heated in the closed tube, the mineral decrepitates, and 

 gives off a little water, which does not redden litmus paper. 

 It readily melts into a brown liquid, which diffuses itself in 

 drops over the contiguous surface of the tube, and on cooling 

 becomes a pale brown fissured mass. 



3. Heated in the open tube, white, not sensibly odorous, 

 vapour is evolved. 



4. Heated in the outer flame of the blowpipe, the flame is 

 green within and deep blue at the edges. 



5. Heated on charcoal in the inner flame, metallic globules 

 are obtained, some having the appearance of lead, others that 

 of copper, or a mixture of copper and lead. 



6. Heated with carbonate of soda on charcoal in the inner 

 flame, metallic globules are obtained, which dissolve without 

 residue in dilute nitric acid. 



Iodide of potassium throws down from this solution a fine 

 yellow precipitate. Ammonia renders it blue. Hydrochloric 

 acid precipitates a minute quantity of white matter, which is 

 insoluble in excess of nitric acid, and becomes slate-coloured 

 by exposure to light. 



7. Heated with borax in the outer flame, a transparent 

 bluish-green bead is obtained, which, in the inner flame, 

 becomes turbid and brownish-red. 



8. The mineral by boiling in nitric acid becomes white and 

 then dissolves. Nitrate of silver precipitates from the solution 

 white curdy matter, insoluble in excess of nitric acid. 



Quantitative Examination. 



It was impossible to separate sufficient of the mineral for 

 analysis ; it was therefore boiled with adhering matrix in 

 successive portions of dilute nitric acid. To the filtered so- 

 lution excess of nitrate of silver was added. The white pre- 

 cipitate, washed and dried at the temperature of incipient 

 fusion, weighed 3'40*. 



♦ After having detached from the filter as much of the dry chloride as 



