482 H. Rein sch on the action of Metallic on Copper Solutions. 



a less metallic lustre, and is of a decided violet colour. With 

 a solution containing l-200,000th part of antimony, the pre- 

 cipitation is so thin that the copper shines through, but has 

 still a violet hue: upon making both precipitates they are 

 easily discriminated by comparison. The delicacy of the re- 

 action is equal to that of arsenic. Antimony also gives no pre- 

 cipitate without the presence of hydrochloric acid, but the 

 addition of a few drops immediately occasions one. 



Tin. — Copper does not occasion a precipitate in a solution 

 of this metal containing l-100th part to which an equal 

 quantity of hydrochloric acid has been added, if kept from the 

 air; on boiling the solution there are slight indications of a 

 metallic precipitate. If exposed to the air in an open vessel, 

 the metal is precipitated after a few days as a grayish black 

 powder : in weaker solutions no precipitate whatever occurs. 



Lead. — With a solution containing 1 -500th part of lead, 

 to which an equal quantity of hydrochloric acid was added, 

 copper produced no precipitate, when kept free from the air; 

 on boiling only a few spots appeared. In dilute solutions 

 there was no action ; on exposure to the air a black powder 

 was precipitated. 



Bismuth. — With a similar solution of bismuth the slip of 

 copper was immediately covered with a grayish metallic coat- 

 ing, when kept free from the air ; this precipitate was gradually 

 converted into small flat crystals; on heating the solution, the 

 copper was immediately covered with a crystalline deposit. 

 The metal was also precipitated from very weak solutions. 



Mercury. — A solution containing l-1000th part of mer- 

 cury mixed with hydrochloric acid, was immediately precipi- 

 tated upon the copper as a white coating. A solution con- 

 taining l-50,000th part of corrosive sublimate without the 

 addition of hydrochloric acid, had no action on the copper 

 when cold ; on heating it produced a golden colour ; on ad- 

 dition of hydrochloric acid and after boiling, the copper had 

 a gray appearance, and metallic mercury might be observed 

 by means of a single microscope. 



Silver.— A solution containing 1 -1000th part of silver, to 

 which hydrochloric acid was added, produced a white coating 

 upon a slip of copper; after twelve hours there were small 

 dendritical crystals formed, which were increased upon heat- 

 ing the solution. A solution containing l-50,000th part of 

 silver without hydrochloric acid, gave the copper a yellowish 

 tinge, which disappeared upon adding hydrochloric acid, but 

 no silver was separated with a solution containing l-20,000th 

 part silver; the metal was precipitated in metallic spots. 



