1822.] Mr. Lunn on Native Phosphate of Copper, 181 



tion the results: the objection to the earthy salts is that unless 

 the solution be most strictly neutral, or even rather alkaUne, a 

 very small quantity of the phosphoric acid enters into insoluble 

 combination; these, therefore, would not answer the intended 

 purpose, because at the very point when the reagent would be 

 useful, the original salt was itself precipitated. 



To the salts of lead then, we must have recourse : the muriate 

 appears to have the preference with Berzelius,* and with this 

 salt accordant results may be obtained ; but both the saline 

 solutions must be most strictly neutral, and the very low degree 

 of solubility of muriate of lead after it has once been crystallized, 

 is a considerable practical inconvenience. With the nitrate of 

 lead I could obtain unvarying results ; it is easily crystallized, 

 and, when carefully washed and redissolved, is perfectly neutral, 

 and of high solubility. 



In both the above methods, it is adviseable to ensure accuracy, 

 that no more of the solution of the salt of lead be added than is 

 necessary to separate the phosphoric acid ; and the precipitate 

 must be boiled in water, by which means the combination of acid 

 mentioned by Berzelius t may be avoided. 



Analysis, 



A portion of the mineral free from any foreign ingredient was 

 reduced to a fine powder : this, after being dried at the temper- 

 ature of 212°, was of a verdegris green colour, and weighed 28*7.. 

 grains. By subjecting it to a low red heat in a platinum crucible, 

 it became ohve-green, more bulky, and lost 2-15 in weight, 

 which was water driven off; it was not adviseable to let it remain 

 long at that heat, for it is capable of being volatilized, which 

 appeared by some condensing on the lid of a crucible. The 

 whole was now dissolved in dilute nitric acid, and formed a clear 

 blue solution ; from this as much water and excess of acid was 

 driven off as possible by a long continued gentle heat. The 

 whole was now very carefully neutralized with a weak solution 

 of potash so as just to avoid the reprecipitation of the salt : 

 nitrate of lead from fresh dissolved crystals was carefully added, 

 avoiding excess, which was shown by the clear hquor above the 

 white precipitate undergoing no change from sulphate of soda, 

 nor hydriodic acid. The precipitate boiled, well washed, and 

 dried, was, after a red heat = 31*23 grains, equivalent to 6*246 

 of phosphoric acid. 



A solution of caustic potash was added in excess, and boiled 

 upon the black precipitate formed ; this when separated and 

 dried at a heat below redness weighed 18*1 grains, and was 

 copper in the same state of oxidation as in the mineral.J 



* Annalcs deChimie, ii. 159. f Ibid. 



X The analysis was also accomplished in another manner, by adding hydrate of 

 aniraonia in such excess as to redissolve the precipitate at first formed. The phosphoric 

 acid was then precipitated by cautiously adding nitrate of barytes, and after the liquor 

 had been rendered acidulous by sulphuric acid, the copper was separated by a plate of 

 r on. The method described in the text has, however, practical advantages. 



