180. Mr, Lunn on Native Phosphate, of Copper. ' [March^ 



Oxide of copper 68*13 



Phosphoric acid 30*95 



And this analysis has been adopted by Haiiy, Brogniart, Thom- 

 son, Jameson, Phillips, and in short copied into every mineralo- 

 gical classification which has appeared. Its accuracy has been 

 doubted,* it is true: for water to the amount of 15 per cent, is 

 overlooked ; but the rarity, of the substance has prevented che- 

 mists from subjecting it to a new examination. 



Having lately received some copper ores brought from a mine 

 at Erpel, near the town of Bonn/f among these were specimens 

 of the mineral in question. In mineralogical characters it agrees 

 with the description of Klaproth. 



In colour it is emerald green, but shaded and streaked with 

 black green, and to this colour the external natural surface 

 approaches ; it is opaque, its powder is verdegris green, it has a 

 diverging striated texture, and a silky lustre ; the specific 

 gravity of one very pure fragment was 4*2 ; its hardness is rather 

 beyond that of malachite. It was in no instance crystallized, 

 although on the external surface of some specimens an imperfect 

 tendency to crystallization was perceptible. It occurs massive 

 in a white opaque quartz rock, in places slightly tinged by oxide 

 of iron ; and it is soluble in nitric acid. By exposure to a red 

 heat in a close crucible, it becomes of a dark olive-green colour, 

 and the powder increases considerably in bulk. Before the 

 blowpipe on charcoal, it readily fuses into a reddish black slag, 

 adhering to the charcoal, and by the addition of carbonate of 

 soda, it is reduced to a bead of pure copper. 



In some specimens, it is accompanied by crystals of phos- 

 phate of lead. 



Although the elements of this mineral are not numerous, yet 

 wherever phosphoric acid enters, considerable caution is neces- 

 sary to ensure correct analytical results : nothing can more fully 

 prove this than the discordancies between the results obtained 

 by two of the most expert analysts. Professors Thomson and 

 Berzelius, and yet both have exerted their utmost skill on this 

 very subject. 



It was necessary to make several previous trials to find out a 

 precipitant which might be depended upon ; or rather, to find 

 out the mode of using^any of the old ones which would produce 

 accordant results. These trials were made upon anhydrous 

 phosphate of soda by barytes, hme, and the salts of lead. I 

 need not repeat a tedious course of experiments, but may men- 



• li'analyse dc M. Klaproth n'indiquc pas que Teau entre dans la composition de ce 

 phosphate, cependant il en contient una quantite assez considerable ; &c. &c. Cette 

 circonstance jette doute sur I'exactitude de Tanalyse de Klaproth; elle merite bien 

 d'etre repetee. Ikrzclius. Nov. Syst. p. 246. Paris, 1819. 



•f- For these vei^ fiue spedmensi, I am indebted to George Samuel Kett, £sq. Brooke 

 House, Norfolk, 



