182 Mir. Lunn on Native Phosphate of Copper, [March, 



Hence 



Phosphoric acid *.. • 6*246 



Peroxide of copper. 18* 1 



Water 2-15 



26-496 

 Loss 2-304 



28-8 



Now this loss would appear considerable, if we do not take 

 into account the impossibiUty of having driven off all the com- 

 bined water, for reasons above stated. If we consider that loss 

 to be water, the result will stand thus : 



Phosphoric acid 6-246 = 21-687 ^ 



Peroxide of copper .... 18-1 = 62*847 iper cent. 

 Water 4-454 = 15-454 J 



28-8 100*000 



Now it is fair, at least, to compare all theory with experimental 

 results ; if we consider the mineral as composed of one atom of 

 phosphoric acid, one atom of peroxide of copper, and two atoms 

 of water, the quantities per cent, will stand as below ; and by 

 the side I have placed the experimental result for comparison. 



Theoretical composition. Experimental result. 



Phosphoric acid 22*222 21*687 



Peroxide of copper 63-492 62-847 



Water 14-285 15*454 



It will be seen that the difference is in no case equal to unity 

 except in the water.* 



If we were to represent the constitution of this mineral by the 

 symbols of Berzehus, which, being derived from the Latin, are 

 more general than the English initials of Thomson, but adopting 

 the opinion of the latter with regard to the constitution of phos- 

 phoric acid. 



Its chemical sign would be C u P 4- 2 A q. 

 Its mineralogical C u P + 2 A q. 



There can be no doubt of Chenevix's artificial phosphate being 

 a biphosphate, as stated by Thomson f ; and it is rather singular 

 that a neutral combination which has not hitherto been formed 

 in the laboratory of the chemist, should be the very substance 

 formed by a natural process in the earth. 



♦ Throughout the«e calailations I have made use of the atomic weight5 recently laid 

 down by Thomson, because in some trials of verification I found them to accord best with 

 experiment. 



+ Thomson's System of Chemistry, vol. ii. p. 607. Fifth Edit. 



