1S14.] Scientific Intelligence. 15/ 



VI. Carbonates of Copper. 



Vauquelin has lately subjected to chemical analysis two species of 

 hvdrous carbonates of copper found at Chessy, near Lyons The 

 first was blue, crystallized, and hard. He found it composed of 



Copper 56 



Oxygen 1 2*5 



Carbonic acid . 25 



Water 6-5 



100-0 



Now as these numbers do not agree with the doctrine of definite 

 proportions, nor with the previous analysis of the same- ore by 

 Klaprotli, 1 think there is reason to suspect some inaccuracy. The 

 proportion of carbonic acid is too great, while that of oxygen is too 

 small. 



The green fibrous ore of copper Vauquelin found composed of 



Copper 56- 1 



Oxygen 140 



Carbonic acid 21 -25 



Water 8*75 



100-10 



This analysis -corresponds much better than the preceding with 

 the doctrine of definite proportions. The quantity of oxygen fount] 

 is correct ; that of the carbonic acid I conceive nearly so. The 

 quantity of carbonic acid which really combines with 7° black 

 oxide of copper is lVr2o7- But unless uncommon precautions are 

 taken, the quantity of carbonic acid driven off from a mineral is 

 apt to be over- rated ; because it carries with it some of the liquid 

 from which it makes its escape. 



VII. Precipitation of Copper hy Iron and Zinc. 

 Vauquelin has published sonic observations on the method of 

 precipitating copper from its solutions by iron or zinc, which may 

 be useful to the young analyst. I shall therefore notice them. 

 Those chemists who have been in the habit of experimenting on 

 i must have been aware of the circumstances which he states. 

 answers better than iron for precipitating copper. Unless the 

 zinc be allowed to remain a sufficiently long time in the solution, 

 the whole copper is not precipitated. Unless there be an excess of 

 Bcid in th>- liquid, a portion of the copper is precipitated in the 

 of oxide. (Ann. de Chim. lxxxvii. lb'.) 1 may add that a 

 portion of zinc always falls in combination with the copper. There- 

 fore the copper, alter the liquid is separated, ought always to be 

 digested in dilute muriatic acid, which takes up the zinc without 

 touching the c pper* 



