AMALGAM 133 



Dahll. It is a hydrous silicate of complex constitution, containing yttria, thoria, 

 zirconia, glucina, alumina, and sesquioxido of iron. 



AMADOU. (Amadou, Fr. ; Zunderschwamm, Ger.) Tho name of a spongy com- 

 bustible substance, prepared from a species of fungus, the Boletus igniarius, -which grows 

 on the trunks of cherry-trees, ashes, beeches, &c. ; it is sometimes known as spunk, 

 and as touchwood, but commonly in this country it is called German tinder. It must 

 bo plucked in the months of August and September. This plant grows horizontally 

 on the several trees on which it is indigenous ; when it makes its first appearance it 

 is a little round wart-like body, not larger than a pea ; it gradually increases in size 

 and hardness till it becomes of a darkish brown, and is as large as an apple. It after- 

 wards takes a horizontal direction, forms a border, and becomes covered with 

 numerous closely-packed tubes on its imder surface. The Boletus fomentarius is 

 another indigenous fungus, found on the oak and birch. This is also used in preparing 

 Amadou. It was formerly used in surgery, and has hence been called Surgeon's 

 Agaric. Amadou is prepared by removing the outer bark with a knife, and separating 

 carefully the spongy substance of a yellow brown colour, which lies within it from 

 the ligneous matter below. This substance is cut into thin slices, and beaten with a 

 mallet to soften it, till it can be easily pulled asunder between the fingers. In this 

 state the boletus is a valuable substance for stopping oozing haemorrhages, and some 

 other surgical purposes. To convert it into tinder it must receive a finishing prepara- 

 tion, which consists in boiling it in a strong solution of nitre, drying it, beating it 

 anew, and putting it a second time into the solution. Sometimes, indeed, to render it 

 very inflammable, it is imbued with gunpowder, whence the distinction of black and 

 brown amadou. 



All the puff-balls of the lycopodium genus of plants, which have a fleshy or fila- 

 mentous structure, yield a tinder by soaking in gunpowder-water. The Hindoos 

 employ a leguminous plant, which they call solu, for the same purpose. Its thick 

 spongy stem, being reduced to charcoal, takes fire like amadou. See AGARIC. 



AlVXAXiGAXMC. "When mercury is alloyed with any metal, the compound is called 

 an amalgam of that metal ; as, for example, an amalgam of tin, bismuth, &c. 



Some amalgams are solids and others fluids ; the former are often crystalline, and 

 the latter may be probably regarded as the solid amalgam dissolved in mercury. 



Silver Amalgam may be formed by mixing finely-divided silver with mercury. The 

 best process is to precipitate silver from its solution by copper, when we obtain it in 

 a state of fine powder, and then to mix it with the mercury. 



A native amalgam of mercury and silver occurs in fine crystals in the mines of 

 Moschellandsberg, in the Palatinate : it is said to bo found where the veins of copper 

 and silver intersect each other. Its existence is also recorded in Hungary and 

 Sweden ; at Allemont, in Dauphine" ; Almaden, in Spain ; Kongsberg, in Norway ; and in 

 Chili ; and the following analyses have been quoted : 



Silver Mercury 



Moschellandsberg . . . 36-0 . . . 64-0 by Klaproth. 



Ditto . . . 25-0 . . . 73-3 Heyer. 



Allemont ..... 27'5 . . . 72'5 Cordier. 



If six parts of a saturated solution of nitrate of silver with two parts of a saturated 

 solution of the protonitrate of mercury are mixed with an amalgam of silver one part 

 and mercury seven, the solution is speedily filled with beautiful arborescent crystals 

 the Arbor Diana, the tree of Diana, or the silver tree. 



Gold Amalgam is made by heating together mercury with grains of gold, or gold- 

 foil ; when the amalgam of gold is heated, the mercury is volatilised and the gold 

 left. This amalgam is employed in the process known as that of fire-gilding, although, 

 since electro-gilding has been introduced, it is not so frequently employed. A gold 

 amalgam is obtained from the platinum region of Columbia ; and it has been reported 

 from California, especially from near Mariposa. Schneider gives its composition, 

 mercury, 57'40 ; gold, 38'89 ; silver, 5'0. 



Tin Amalgam. By bringing tinfoil and mercury together, this amalgam is formed, 

 and is used for silvering looking-glasses. If melted tin and mercury are brought 

 together in the proportion of three parts mercury and one part tin, the tin amalgam 

 is obtained in cubic crystals. See SILVEBINO GLASS. 



Electric Machine Amalgam. Melt equal parts of tin and zinc together, and add 

 three parts of mercury ; the mass must be shaken until it is cold, and rubbod down 

 with some lard to give it the proper consistence. 



Sodium Amalgam, used for separating gold from its ores. See GOLD, SILVER. 



Copper Amalgam. The French dentists have long made use of this for stopping 

 teeth. It is sold in small rolls of about a drachm and a half in weight; it is covered 

 with a greyish tarnish, has a hardness much greater than that of bone, and its cohesion 



