298 Intelligence and Miscellaneous Articles, 



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the hydrated acid ; when it is sublimed, as first shown by M. Gui- 

 bourt, it becomes anhydrous. M. Malaguti obtained the anhydrous 

 acid in a different manner ; by decomposing camphovinic acid by 

 distillation, he converted it into anhydrous camphoric acid and cam- 

 phoric aether. He has also verified the composition of camphoric 

 acid by analysing camphovinic acid, camphoric aether, camphorate 

 of ammonia, silver, &c. He has observed that hydrous and anhy- 

 drous camphoric acid produce salts sensibly different from each other, 

 although dissolved in water, in the same manner as phosphoric and 

 pyrophosphoric acid. He has also observed that camphoric acid in 

 solution does not form a neutral ammoniacal salt ; that, in order to 

 obtain this salt, it is requisite to expose the crystallized hydrated 

 acid to ammoniacal gas until absorption ceases, in the same manner 

 as performed by M. Robiquet with gallic acid. 



M. Laurent has also obtained results perfectly similar to those of 

 Malaguti, respecting the composition of camphoric acid ; but they 

 were not published so soon. — Journal de Chimie Medicale, November 

 1837. 



ON THE COLOURS OF METALS. BY MONS. R. BOTTIGER. 



It has long been known, that when very fine copper filings are put 

 into a vial, and they are covered with a saturated solution of hydro- 

 chlorate of ammonia, in 24 hours a colourless solution is obtained, 

 provided only one-third of the vial contains air, and that it is well 

 stopped and frequently shaken ; this solution, when exposed to the 

 air, instantly becomes of a fine sky-blue colour, and is again ren- 

 dered colourless by being again strongly shaken in the vial with the 

 copper filings. 



This liquid is a solution of ammoniacal chloride of copper ; and if 

 a slip of polished platina be put into it, no change is perceptible ; 

 feut if, at the same time, it be touched with a piece of zinc, its sur- 

 face, whatever may be its extent, becomes then completely covered 

 with a very thin stratum of copper, and this disappears quickly, as 

 soon as the platina is separated from the zinc. This fact is readily 

 explained when it is remembered that the liquor contains a consider- 

 able quantity of free ammonia. If also, instead of exposing the 

 coated platina to the action of the ammoniacal liquid, it be immersed 

 in a vessel of water, as soon as the coating of copper appears, it re- 

 mains fixed on the platina, notwithstanding it may be agitated in 

 the water. 



If, instead of removing the platina from the contact of the zinc as 

 soon as the copper appears, this action is suffered to continue for a 

 longer time, for example, during one or two minutes, bubbles of gas 

 are given out, and copper is deposited in spite of its electro-positive 

 state, the colour of which is no longer red, but, on the contrary, ap- 

 pears black. At the same time, the red colour of the shp of platina, 

 derived from the deposit of copper, which was at first fixed upon it, 

 disappears, and in its place there arise various shades of all colours 

 possessing remarkable beauty. Some are yellow, others green, others 



