SQ-t Intelligence and Miscellaneous Articles. 



COMBUSTIBILITY OF CARBON INCUEASEU BY VLATINA AND 

 COPPER. 



The following experiment is due to Washier : — Rasped cork is to 

 be heated in close vessels with ammonio-muriate of platina, or 

 verdigris, when a charcoal will be obtained, wliich, though it will not 

 inflame spontaneously, does so if slightly heated, and then continues 

 to burn of itself. The cliarcoal obtained from cork without these 

 additions, does not inflame at so low a temperature, nor continue to 

 burn in small masses, if once .inflamed .and left to itself. 



This effect is analogous to that discovered by Doebereiner, as be- 

 longing to platina; but as regards copper, a more curious one of the 

 same nature is shown very ea^-iiy by a common green wax taper. 

 Tliese tapers are coloured witli verdigris, and when burnt, the copper 

 of the verdigris is reduced for a time on the wick. If such a taper 

 be lighted, and the flame then blown out, leaving the wick glowing, 

 combustion of the wax v,'ill still proceed, slowly indeed, but for hours 

 and days together, until the whole of the v/ax is burnt, or until the 

 combustion has reached some part where it is extinguished by the con- 

 tact of neighbouring bodies. This does not happen with wliite tapers, 

 and hence they are safer for ordinary uses. — Royal Inaiitule Jouinal, 

 October 1829. '■ — 



M. ORFILA ON IMR. SMITHSON's MODE OF DETECTINa 

 MERCURY. 



In the Annals of Philosophy, vol. iv. p. 127, N.S., Mr. Smithson 

 has proposed to detect very minute quantities of arsenic and mer- 

 cury ; he states that all the oxides and saline compounds of mercury 

 laid in a drop of muriatic acid on gold with a bit of tin, quickly 

 amalgamate the gold ; and he asserts that quantities of mercury may 

 be rendered evident in this way, which could not be so by any other 

 means. 



M, Orfila having occasion to examine a syrup supposed to contain 

 mercury, attempted to discover it by Mr. Smithson's voltaic pile. 

 At first he was inclined to suppose that mercury was detected by it, 

 but having himself prepared some of the syrup into which no mercu- 

 rial salt whatever was put, he found that when acidulated with a few 

 drops of muriatic acid, the gold became white in twenty-four hours, 

 and tiie fire acted upon it as if it had been covered with mercury. 



On examination it was found that on putting the small pile into 

 four ounces of water, acidulated with fifteen drops of muriatic acid, the 

 gold became white in twenty-four hours even in some parts untouched 

 by the tin. When heated the gold recovered its usual colour ; when 

 the gold and tin not in contact were placed in this mixture, the gold 

 suffered no alteration. An ounce and a half of distilled water contain- 

 ing only twelve drops of a saturated solution of common salt, caused 

 white spots upon the gold of the pile in twenty-four hours ; these 

 were proved to be tin. The gold and tin put not in contact into a 

 mercurial solution do not act. When gold is whitened by tin it is 

 readily removed by muriatic acid, but this is not the case when the 

 change has been effected by mercury ; but a more certain method, 

 according to M. Orfila, consists in placing the piece of gold at the 



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